tolong jawab dong sama caranya sekalian

f(x)= 7-2x
f(a)=7-2(a)=-9
       7-2a=-9
       7+9=2a
         16=2a
          8=a
a-5=8-5=3

f(x) = 7-2x
f(a) = -9

-9 = 7-2a
-9-7 = -2a
-16 = -2a
8 = a

a-5
8-5 = 3

jawabannya A