f(x) = 24 - 2x
f(2) This means that x is 2, so you can plug in 2 for x
f(x) = 24 - 2x
f(2) = 24 - 2(2)
f(2) = 24 - 4
f(2) = 20
To find x when f(x) = 10, you can do:
f(x) = 24 - 2x [substitute/plug in 10 for f(x)]
10 = 24 - 2x Subtract 24 on both sides
-14 = -2x Divide -2 on both sides
7 = x