12.56 ÷ 3.14 = 4cm

4÷2 = 2 cm

2x2x3. 14= 12.56 cm2

2.

Solution: There are X 8-point stamps and (X-25) 4-point stamps.

0.08X+(X-25)x0.04=8

0. 12X- 1=8

0. 12X=9

X=75

A: There are 75 8-cent stamps.

3.

Set x pen and 9-x ballpoint pen.

3x+2(9-x)=23

x+ 18=23

x=5

9 x = 4