2x+32= 1 152
2x= 1 152-32
x= 1 120÷2
x=560
2) solution: let each pen be x yuan.
3x+2x=40
5x=40
x=40÷5
x=8
3) solution: catch up after leaving x hours.
15x = 12x+ 12×3/4
15x- 12x=9
x=9÷3
x=3