Trying to understand this, someone help pls thank you !

Actually Welcome to the concept of Lines.

We know that perpendicular lines have a inverse negative slope, such that

m1*m2 = -1

hence, m1 = -1/m2

so the perpendicular line is,

==> y-(5) = 3/2(x-(-6))

==> y+5 = 3/2(x+6)

==> y+5 = 3/2*(x) +9

=> y = 3/2(x) +9-5

==> y = 3/2*(x) + 4

hence the correct option is D.)