A)5X18=5X2X4=5X2X9=10X9=90
5X36=5X6X6=30X6=180
2X45=2X5X9=10X9=90
5X16=5X4X4=20X4=80
B)36X75=4X9X3X25=(4X25)X(9X3)=100X27=2700
24X75=4X6X3X25=(4X25)X(6X3)=100X18=1800
28X75=4X7X3X25=(4X25)X(7X3)=100X21=2100
36X25=4X9X25=(4X25)X9=100X9=900
28X25=4X7X3X25=(4X25)X7=100X7=700