Finding the Value of an Expression Video Lecture - for Grade 7

hi this is mrs. fry Feld and today I
want to help you with evaluating
algebraic expressions recall that an
algebraic expression contains one or
more variables which are the letters
that you see in the problems
you can substitute a number for that
variable and then find the value of the
expression this is called evaluating the
expression we're going to evaluate each
expression for the given value of the
variable
here's your algebraic expression X is
your variable but over here it tells you
what the value of x is so you rewrite
this expression and where you see the
variable X you replace it with 15 so
it's 15 minus 5 and the answer to that
is 10 let's try it again here's all our
algebraic expression our variable is n
but in this case it gave you the value
of the variable so N equals 8 so I'm
going to rewrite this expression and
where it has n I'm gonna put 8 well I
can see that this is now an improper
fraction and all I have to do to solve
it is tebow it and the answer is 2 I
want you to get a communicator and see
if you can do this one on your own
before I tell you the answer pause the
pause the video now
okay I see that my algebraic expression
is here here's my variable and I look
over here and it tells me that where I
see the variable Y I'm gonna replace it
with a number three so I have now
rewritten that algebraic expression and
where why was I have the three and I use
the order of operations to solve it I
solve multiplication before addition 2
times 3 is 6 and then 6 plus 5 there's
only one operation left and the answer
is 11 again
go ahead and pause the video and see if
you can do this by yourself here's my
algebraic expression I have 6 times the
variable K and over here it says K
equals 1/3 first I rewrite the algebraic
expression but where K is I put in 1/3
and because now I replace it with a
number I need to go ahead and put the
multiplication sign between these two
numbers
well when I'm trying to multiply a whole
number by a fraction I need to rewrite
the whole number is a number over 1
times that fraction and then I just
multiply first the numerators and then I
multiply the denominators and that
equals 6 over 3 that's improper I tebow
it and my answers to again pause the
video and see if you can do it by
yourself and then unpause it to find out
the answer my algebraic expression is
here the variable is s and it's giving
me the value of the variable so I
rewrite the algebraic expression and
where I see s I replace it with 2
because I went in and put the number 2
in for s I need to put the operation
that was going on between the 3 and the
s and that's multiplication now I use
the order of operations and I multiply
first 3 times 2 is 6
and now there's only one operation left
and the two of those equals seven again
I want you to pause the video and see if
you can do this by yourself here's my
algebraic expression and my variable is
N and then over here I see that they
gave me that the value of n is negative
two so I rewrite the expression with
negative 2 where n was and because I
replace this n with a number I need to
put a multiplication sign between the
two of them and now I use my order of
operations to solve it the first thing I
do is multiply a positive times a
negative is a negative so 4 times
negative 2 is negative 8
I bring the rest of the problem down and
now there's only one operation I see
that these signs are the same so I add
them and I use the sign in front of the
biggest digit the answer to this problem
is negative 12 good job guys
see you next time