The first one can be divided into trapezoid and rectangle. The second type can be divided into trapezoid and triangle. The third type can be divided into rectangles and triangles.

The fourth can be divided into two triangles. The fifth type can be divided into square and trapezoid.

(1) (5+10) × (12-6) ÷ 2+6× 5 = 45+30 = 75 (square centimeter)

(2)10× (12-6) ÷ 2+(6+12) × 5 ÷ 2 = 30+45 = 75 (square centimeter)

(3) (10-5) × (12-6) ÷ 2+12× 5 =15+60 = 75 (square centimeter)

(4)12×10 ÷ 2+6× 5 ÷ 2 = 60+15 = 75 (square centimeter)

(5)12×10-(6+12 )× (10-5) ÷ 2 =120-45 = 75 (square centimeter)