3mn+12m+9mn=
5XY+10X-20XY=
20tu-10tz-4tx=
18ab-9bc+4bd=
8pq+4qr-2qm=
2t(10u-5z-2x)
3m(n+4+3m)
5X(Y+2X-4Y)
b(18a-9c+4d)
2q(4p+2r-m)
