15.37×7.8-9.37×7.8+15.84×2.2-9.84×2.2
=(15.37-9.37)X 7.8 + (15.84-9.84)X 2.2
=6 X7.8 + 6 X 2.2
=6 X (7.8+2.2)
=6X10
=60