Question

15 more than half a number is nine

Answer 1

15+1/2n=9
1/2n=9-15 (subtract 15 from both sides)
1/2n=-6
n=-6/(1/2) (divide both sides by 1/2)
n=-12 (answer)

Answer 2

(1/2)x+15 = 9
(1/2)x= -6
x = -12