Question

x+2y=17 y-3z=4 calculați x+3y-3z

Answer 1

x + 2 y = 17    si    y - 3 z = 4

x + 3 y - 3 z = 21

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

= 17 + 4 =

= 21

Answer 2

x+2=17 ; y-3z=4 ; x+3y-3z=(x+2y)+(y-3z) = 17+4 = 21