the quotient of a number (n) and 4 is written as  n/4

nine more means addition. n/4 + 9

so you have the following equation.

n/4 + 9 = 12

then solve for n

n/4 + 9 - 9 = 12 - 9

n/4 = 3

n/4 x 4 = 3 x 4

n = 12