He can use:
a quarter and a dime (difference: 15)
a quarter and two nickels (difference: 20)
a dime and three nickels (difference: 5)
two dimes and a nickel (difference: 5)
Answer:

Step-by-step explanation:

Adding 9x & 3x gives 12x.

Now taking 4 common from both the terms , we get :-

Answer:
it would be a fraction of a sec
Step-by-step explanation:
see if you just simply took out a calculator you would see its not possible unless you knew what the balloon is descending at during the fraction of the seconds
Answer is in the file below
tinyurl.com/wpazsebu