Answer: 42
Plug in x = -5. Then use PEMDAS to simplify
f(x) = -9*x - 3 ... original function
f(x) = -9*( x ) - 3 .... parenthesis help with the next step
f(-5) = -9*( -5 ) - 3 ... replace every x with -5
f(-5) = 45 - 3 ..... multiply
f(-5) = 42 .... subtract