Hello from MrBillDoesMath!
Answer: the lines are not perpendicular (as stated by another writer)
Steps:
Rewrite the first line (2x -y = 5) as y = 2x -5. So it's slope, m1, is "2"
Rewrite the second line ( -1/2x + y =3 ) as y = +1/2x + 3. So it's slope, m2, is +1/2.
Two lines are perpendicular if m1 * m2 = -1 which is NOT the case here (For us, m1 * m2 = 2 * (+1/2) = + 1 which is not -1. As they say, "close, but no cigar!)
Regards, MrB