1) solution: suppose that the price of each piece is reduced by X yuan, the profit of each piece is 40-X, and the sales volume is 20+2X.

By the known y=(40-x)(20+2x)

Namely: y=-2x? +60x+800

2) when y= 1200

200=-2x？ +60x+800

Solution: x 1= 10 x2=20.

A: Every shirt should be reduced by 10 yuan or 20 yuan.

3) If the price of each shirt is reduced by Y yuan, the mall will make a profit of Z yuan every day. Then z = (20+2y) (40-y) =-2y2+60y+800 =-2 (y-15) 2+1250, ∴ Y = 60.