Tony paid $7 - $5 = $2 more than Arnold. We know he bought the same number of bananas as Arnold but that he bought 2 - 1 = 1 dozen apples more than Arnold. Therefore a dozen apples should cost $2. If Arnold paid $5 and $2 for a dozen apples then the bunch of bananas cost $5 - $2 = $3.
The answer: 3
Reverse engineering the question: Tony paid $7 for 2 dozen apples and 1 bunch of bananas. Arnold paid $5 for 1 dozen apples and 1 bunch of bananas. How much does a bunch of bananas cost?

Together, they picked 30 * 3 = 90. There are 40 + 28 = 68 accounted for. Then Layla picked 90 - 68 = 22.
The answer: 22
Reverse engineering the question: Maggie picked 40 apples. Kelsey picked 28 apples. Layla picked some apples, too. The three averaged 30 apples picked. How many did Layla pick?

It rained 3 + 4 = 7 inches. So he collected 7 * 15 = 105 gallons. So he makes 105 * 1.2 = $126 from selling the water.
The answer: 126
Reverse engineering the question: James has a rainwater collection barrel. For each inch of rain he collects 15 gallons. On Monday it rained 4 inches and on Tuesday it rained 3 inches. He can sell water for $1.2 per gallon. How much money did he make from selling all the water?

The quarters came to 4 * 25 = 100 cents. The dimes were worth 3 * 10 = 30 cents. The nickel was 5 * 1 = 5 cents. So he paid 100 + 30 + 5 = 135 cents. Since he got 4 cents as change it cost 135 - 4 = 131 cents.
The answer: 131
Reverse engineering the question:
John pays for a candy bar with 4 quarters, 3 dimes, and a nickel. He got 4 cents back in change. How many cents did the candy bar cost?