4x-3y=0 5x+5y=20 hasilnya adalah

5x + 5y = 20 (x3)
4x - 3y = 0 (x5)

15x + 15 y = 60
20x - 15y = 0
______________(+)
35x = 60
x = 60/35 = 12/7

4x - 3y = 0
4x = 3y
4x = 3(12/7)
4x = 36/7
x = 36/7 x 1/4
x = 36/28 = 9/7

semoga membantu