Math problems in the fifth grade of primary school, such as how many square centimeters the area of A is more than that of B.
A+ blank =6× 12=72 (square centimeter)
B+ blank =(3+6)× 12÷2=54 (square centimeter)
So,
A-B =(A+ blank) -(B+ blank)
=72-54
= 18 (square centimeter)