1. Let the price be X, the cost be Y, and the selling price-cost = profit.

Then two types can be listed:

( 1) 0.5x-y=-20

(2) 0.8x-y=40

The two formulas are subtracted to get x=200 (that is, the price tag).

Substitute the value of x into any formula and calculate the cost y= 120.

2. Set the maximum discount of Z to ensure no loss, that is, the price cost > =0.

The formula is 200 z-120 > =0,

Then z & gt=0.6,

That is, the maximum discount is 60%.

Is that clear? You can contact me again if you don't understand!