Profit W=5X+ 10( 100-X)
According to the meaning, we can get 750 ≤ 5x+10 (100-x) ≤ 760.
The solution is x=48≤X≤50, so a is: x = 48,49,50b is: 52,565,438+0,50.
There are three purchase plans.
① A 48 B 52
② A 49 B 5 1
③ A 50 B 50
(The most profitable option is Option 1)
(3) Day 1: No discount. Therefore, to buy a commodity: 200÷20= 10 (piece)
The next day: discount.
①324÷0.9=360 (yuan) for the second commodity: 360÷45=8 (pieces).
* * * Bought 18 items from Party A and Party B. ..
②324÷0.8=405 (yuan)
405÷45=9 (pieces)
So * * * bought 19 items from both parties.