In the equation y = 4 x, if the value of x is increased by 2, what is the effect on the value of y ?

Answer 1

well, just plug it in and see what you get:

y = 4(x+2) = 4x+8

so, y increases by 8.

You could also have seen this by noting that the slope is 4, meaning that every time x increases by 1, y increases by 4.