Question

which is a zero of the function defined by the following equation: f(x)= 5x-20

Answer 1

So, if you graph it, the y-intercept is at -20 and the slope is 5. It will hit your zero(s) at the x-intercept of x=4

Answer 2

f(x) = 5x - 20
5x - 20 = 0
    + 20  + 20
       5x = 20
        5      5
         x = 4