Question

Find a liner equation f(x) with slope 5 such that f(3)=12

Answer 1

f(x) = mx + b, where m is the slope.
Then, plug f(3) into the equation where x = 3
12 = 5(3) + b
and solve for y-intercept.
After you have found the y-intercept, put your equation together and that should be the answer.