TEST LOGIC MATH SPLTV 2014

TEST LOGIC MATH SPLTV
Are You Ready ? 

Jika Diketahui
2x + y = 20
2y + z = 22
z - x = 2
y + a = 10
Maka nilai dari z - x + y - a adalah ?
 
Solusinya :
z = 2 + x

2y + 2 + x = 22
2y + x = 20

2x + y = 20
4y + 2x = 40
---------------------- -
3y = 20
y = 20/3
x = 20/3
z = 26/3

y + a = 10
a = 10 - y
a = 10/3

z - x + y - a = (26 - 20 + 20 - 10)/3 = 16/3