Write an equation for the line that passes through (0,7) and is perpendicular to the line whose equation is y = 1/2x-1.

my answer is y = 2x-7 is this correct?

That can't be right, because when x=0, y must be 7.

Furthermore, the slope of the line you want must be -2, to be perpendicular to
y = x/2 -1, a line with slope 1/2.

Your equation has a slope of 2, not -2.

The correct answer is
(y-7)/(x-0) = -2
y = -2x + 7