B.
Using this will give you proper representations in similar triangles.
A. F(x)= 3x+6 =12
3x = 12-6
3x = 6
x=2
B. x=10, f(x)= 3*10+6 = 30+6 = 36
C. f(x) = 3x+6 = 6
3x = 6-6
3x=0
x=0
D. x=5, f(x) = 3x+6 = 3*5+6 = 15+6 = 21
You might be able to do direct substitution.
I think they should keep it around, even if it might not be the most efficient strategy. After all, what if you need to solve a problem using multiple strategies?
