Question

Each of Steve's buckets has a capacity of 11 gallons, while each of Mark's buckets can hold 8 gallons. How much more water in gallons can 7 of Steve's bucket's hold compared to 7 of Mark's buckets?

Answer 1

You need to know the difference between seven 11gal buckets, and seven 8gal buckets.
$x=7\times11gal-7\times8gal$
but that sounds like a lot of math, lets make it simpler.
$x=7(11)-7(8)\\x=7(11-8) \\ x=7(3)\\x=21$