Okay so the equation. Lets say e is explorers and v is flying vs and m = money.
e + v > or = 30.
80e + 5v =m.
e < or = 20\
v < or = 20.
Okay, the most money he could make would be if he made 20 explorers at 80 dollars and 10 vs at 5 dollars.
Total money...
1600 + 50 = 1650.
So he could make $1650.
The answer is 62 with a remainder of 2.
Hope this helps!
Answer:3 boxes.
Explanation: $21 / $7=3 boxes