so first write the equation in slope intercept form y=mx+b
5x-2y=7
5x=2y+7
5x-7=2y
5/2x-7/2=y or y=5/2x-7/2
now that you know the slope(5/2x) of the equation all you do change the slope to the negative reciprocal which is -2/5x-------> the answer you're looking for
