To solve the equation 3a = 15, we need to isolate the variable 'a' on one side of the equation. This can be done by using inverse operations, which are operations that undo each other.

Step 1: Understand the Equation
The given equation is 3a = 15. Here, 'a' represents a number, and we need to determine its value.

Step 2: Identify the Operation
The equation involves multiplication, as 3 is multiplied by 'a' to give 15.

Step 3: Apply the Inverse Operation
To isolate 'a', we can use the inverse operation of multiplication, which is division. By dividing both sides of the equation by 3, we can cancel out the multiplication and solve for 'a'.

Step 4: Divide Both Sides by 3
Dividing both sides of the equation by 3, we get:

3a/3 = 15/3

Simplifying, we have:

a = 5

Therefore, the solution to the equation 3a = 15 is a = 5.

Step 5: Check the Solution
To verify if the solution is correct, we substitute the value of 'a' back into the original equation and see if both sides are equal.

When we substitute a = 5 into the equation 3a = 15, we get:

3(5) = 15

Simplifying, we have:

15 = 15

Since both sides are equal, we can conclude that the solution a = 5 is correct.

Summary:
To solve the equation 3a = 15, we divided both sides of the equation by 3. This allowed us to isolate the variable 'a' and determine its value, which is 5. We then checked our solution and found that it satisfies the original equation.