using elimination method:
3x - 5y = 9 ----equation 1
4x + 8y = 12 ----equation 2
multiply equation 1 with 4 and equation 2 with 3
(3x - 5y = 9) x 4
12x - 20y = 36 ----equation 1'
(4x + 8y = 12) x 3
12x + 24y = 36 ----equation 2'
subtract equation 1' from equation 2'
12x + 24y = 36
- 12x - 20y = 36
44y = 0
y = 0
multiply equation 1 with 8 and equation 2 with 5
(3x - 5y = 9) x 8
24x - 40y = 72 ----equation 3
(4x + 8y = 12) x 5
20x + 40y = 60 ----equation 4
add equations 3 and 4
24x - 40y = 72
+ 20x + 40y = 60
44x +0y = 132
44x = 132
x = 3
