X/(3x-9y) = -70 -> 1/(3x-9y) = -70/x
1/(3x-9y) + x = 3
-70/x + x = 3
-70 +x^2 - 3x = 0
(x - 10)(x + 7) = 0
a) x = -7
1/(-21 - 9y) = 10
9y + 21 = -0.1
9y = -21.1 = -18 - 31/10
y = -2 - 31/90
b) x = 10
1/(30 - 9y) = -7
30 - 9y = -1/7
9y = 30 + 1/7 = 27 + 21/7 + 1/7
y = 3 + 22/63
x1 = -7, y1 = -(2 + 31/90)
x2 = 10, y2 = 3 + 22/63