ANSWER
Find out the how tall are two boxes and microwave are combined.
To proof
As given
One box is 3 feet 8 inches tall,
other box is 4 feet 10 inches tall,
microwave is 3 feet 7 inches tall.
tall combined = one box tall + second box tall + microwave tall
= 3 feet 8 inches + 4 feet 10 inches + 3 feet7 inches
= (3 feet + 4 feet + 3 feet) ( 8 inches +10 inches + 7 inches)
= 10 feet 25 inches
Hence proved