Simple....
first set up an equation....
y=12x+120
Now there's two ways you can solve this plug n chug...or set them equal..
First we will plug n chug...
A.)26
y=12x+120
y=12(26)+120
y=312+120
y=432 (No)
B.)34
y=12x+120
y=12(34)+120
y=408+120
y=528 (No)
C.)44
y=12(44)+120
y=528+120
y=648 (No)
D.)24
y=12x+120
y=12(24)+120
y=288+120
y=408 (Yes)
The other way is setting it equal to...
12x+120=408
Isolate the variable...
12x+120=408
-120 -120
12x=288
x=24
Thus, your answer.