Jumlah dari x-3y+5 dan x+y-7 adlh

X-3y+5+x+y-7=x+x-3y+y+5-7
=2x-2y-2
=2(x-y-1)

( x – 3y + 5) + (x+y-7) = x – 3y + 5 + x + y – 7
                                 = 2x – 2y -2