Let the number at tens place be x and the number at ones place be y.

then the number will be=
(10x+y)
number obtained after reversing its digits=
(10y+x)

A.T.Q.

x - y= 3. ---------(i)

(10x + y)+(10y + x)=143
11x + 11y=143
11(x+y)=143
x + y=143/11
x + y=13. ---------(ii)

adding both equations, we get;-

x - y + x + y=13+3
2x=16
[x=8]

putting value of x in (i)

8-y=3
y=8-3
[y=5]


now our original number will be:-

=10x + y
=10×8+5
=85

hence original number will be 85.

Thank you.. :-)

Problem Analysis:
Let's represent the original two-digit number as 10x + y, where x and y are the tens and units digits, respectively. According to the problem, the digit in the tens place is greater than the digit in the units place by 3, so x = y + 3.

When the digits are interchanged, the resulting number is 10y + x. Adding this number to the original number gives us a sum of 143, so we have the equation:

(10x + y) + (10y + x) = 143

Simplifying this equation, we get:

11x + 11y = 143
x + y = 13

Solution:
To solve this problem, we can use substitution or elimination method.

Substitution Method:
Substituting the value of x from the first equation into the second equation, we have:
y + 3 + y = 13
2y + 3 = 13
2y = 10
y = 5

Substituting the value of y into the equation x = y + 3, we have:
x = 5 + 3
x = 8

Therefore, the original number is 10x + y = 10(8) + 5 = 85.

Elimination Method:
Adding the first and second equations together, we have:
(10x + y) + (10y + x) = 143
11x + 11y = 143

Dividing both sides of the equation by 11, we get:
x + y = 13

Subtracting this equation from the first equation, we have:
(11x + 11y) - (x + y) = 143 - 13
10x + 10y = 130

Dividing both sides of the equation by 10, we get:
x + y = 13

Since this equation is the same as the second equation, we can conclude that it has infinitely many solutions. However, if we consider the additional condition that the digits must be different, then the only solution is x = 8 and y = 5.

Therefore, the original number is 10x + y = 10(8) + 5 = 85.

Conclusion:
The original two-digit number is 85.