Write the equation of the line with an x-intercept at (4,0) and parallel to y=1/2x-7

I will assume that by your "y=1/2x-7" you actually meant y = (1/2) x-7; here (1/2) is the coefficient of x.

The slope of this line can be read off immediately: m = 1/2.

Now insert into the general slope-intercept form y = mx + b the knowns m, x and y:

0 = (1/2) (4) + b. Then b = - 2, and y = (1/2) x - 2 is the desired equation of the line.