x+y=6.5
25x=40y
The solution is x=4 y=2.5.
(2) If the Z-box of toy A is purchased, the box of toy B is purchased (100-z).
100-z≤40
8 * 15% * 10z+5 * 10% *( 100-z)≥900
There are 2 1 in 23 cases with z≥ 73, so at least 74 boxes of Class A toys were bought.