the slope of perpendicular lines are always the opposite sign of each other. We know that the slope of the given line is 1/2, so the slope of its perpendicular line will be -1/2
now, we can use point slope form to find the equation.
y-y1 = m(x-x1)
y-10=-1/2(x-7)
y-10 = -1/2x + 7/2
y= -1/2x + 7/2 + 10
y = -1/2x + 27/2