diketahui a=x-y,b=y-z,c=x+y-2z tentukan hasil opersai aljabar 2c-a-4b! plis jawab,besok kumpulin

Here's the answer. Thank you

a = x - y
b = y - z
c = x + y - 2z

2c - a - 4b = 2(x+y-2z) - (x-y) - 4(y - z)
= 2x +2y - 4z - x+ y - 4y + 4z
= 2x-x + 2y+y-4y - 4z + 4z
= x - y