Решить систему уравнений 3u-4v=2 9u-5v=7

3u-4v=2, 9u-5v = 7
-9u+12v= -6, 9u-5v = 7
(-9u+12v)+ (9u-5v) = -6+7, 7v = 1, v = 1/7

15u-20v = 10, -36u + 20v = -28
(15u-20v) + (-36u+20v) = 10 + (-28), -21v= -18, u = 6/7