Find the equation of the line that is perpendicular to 2x-5y=20 and passes through the point (7,-8

Hello : 
2x-5y=20
calculare the slope: 
5y = 2x-20
y =(2/5)x -4 
the slope is (2/5).
let : a   the slope of the line perpendicular to 2x-5y=20 
 a×(2/5) = -1
a = -5/2
an equation is : y+8 = (-5/2)(x-7)... (equation in point slope form )