Question

The product of a number and three is added to six. The result is fifteen. What is the number?

Answer 1

The number is 3
3x3=9 
9+6=15

Answer 2

Product of number added to six is fifteen
3n + 6 = 15
take 6 to the right side
3n + 6 - 6 = 15 - 6
3n = 9

Divide by 3 to isolate the unknown number n
$\frac{3n}{3} = \frac{9}{3}$
3 and 3 cancels out
n = 3

The number is 3