1)
2x/3 - 3y/4 = 11/12
4x/12 - 9y/12 = 11/12
4x - 9y = 11 or x = (9y + 11)/4
2)
x/3 + 7y/18 = 1/2
6x/18 + 7y/18 = 9/18
6x + 7y = 18
substitute eq(1) into eq(2):
6[(9y + 11)/4] + 7y = 18
13.5y + 16.5 + 7y = 18
20.5y = 1.5
y = 1.5/20.5 = 3/41
using eq(1):
x = (9(3/41) + 11)/4
x = [(27/41) + 11]/4
x = (478/41)/4 = 478/164 = 239/82