Question

calcule: (x- 2 y ) +(2 x +2z - y ) - ( y + x - 3z)

Answer 1

(x-2y)+ (2x+2z-y) - (y+x-3z) = 
= x - 2y + 2x + 2z -y - y - x + 3z =
= x + 2x - x - 2y - y -y  + 2z + 3z = 
= 2x - 4y + 5z