Jika x + 2y =3a +5 dan 2x - y = a + p maka 10x - 10y adalah

x + 2y = 3a + 5
x = 3a + 5 - 2y

2x - y = a + p
2(3a + 5 - 2y) - y = a + p
6a + 10 - 4y - y = a + p
6a + 10 - 5y = a + p
5y = 6a + 10 - a - p
y = 5a/5 + 10/5 - p/5
y = a + 2 - p/5

x = 3a + 5 - 2y
x = 3a + 5 - 2 (a + 2 - p/5)
x = 3a + 5 - 2a - 4 + 2p/5
x = a + 1 + 2p/5

10x - 10y = 10 (a + 1 + 2p/5 ) - 10 ( a + 2 - p/5)
= 10a + 10 + 20p/5 - 10a - 20 + 10p/5)
= -10 + 30p/5
= -10 + 6p atau = 6p - 10