Water Balloons

Riddle: Robert and David were preparing to have a water balloon fight. "No Fair" cried Robert, "You have 3 times as many as I do!" David said "Fine!" and gave Robert 10 more balloons. "Still not fair!" argued Robert, "You still have twice as many as I do." How many more balloons must David give Robert for them to have the same number?

Answer: David must give Robert another 20 water balloons, giving them each 60. Robert started with 30 water balloons and David with 90.

Source: https://www.riddles.com/421

Robert and David were preparing to have a water balloon fight. "No Fair" cried Robert, "You have 3 times as many as I do!" David said "Fine!" and gave Robert 10 more balloons. "Still not fair!" argued Robert, "You still have twice as many as I do." How many more balloons must David give Robert for them to have the same number? — Water Balloons by Anonymous v1.

Riddle: Robert and David were preparing to have a water balloon fight. "No Fair" cried Robert, "You have 3 times as many as I do!" David said "Fine!" and gave Robert 10 more balloons. "Still not fair!" argued Robert, "You still have twice as many as I do." How many more balloons must David give Robert for them to have the same number? Answer: David must give Robert another 20 water balloons, giving them each 60. Robert started with 30 water balloons and David with 90. — by Anonymous v2.