Question

I have this weird question that has to do with linear equations (I think), and this is what it says. Let f(x) = 4x - 5 A. Find f(3) B. Find x when f(x) = -21 Can somebody help me understand this ? ?

Answer 1

`f(3)=4\cdot3-5=12-5=7\\\\ 4x-5=-21\\ 4x=-16\\ x=-4`