Answer: 21 cups.
Explanation:
1. Find how much he earns every cup, then use this rate to find how many cups he needs to sell to get $42.
2. He earns $8 per 4 cups, so to find out how much one cup is, we divide.
8/4 =2
3. Use the rate of 2 to find how many cups he has to sell to get $42.
If he earns $2 per cup and wants to earn $42, number of cups he has to sell is 42/2
42/2=21.
As an equation:
(8/4) = (42/x)
2=42/x
2x=42
x=21
Hope this helped