How do i solve the problem f (x) = 7x+8

If you just want to find the roots / x-intercept, you just have to plug in 0 for y

0=7x+8

8=7x

8/7=7x/7

8/7=x

8/7 is the root / x-intercept / solution

If you want to find the y intercept, just by looking at the equation you can find it. Since it's in slope intercept form, the y intercept is 8.