a) Brent has least amount of money (because he has more number of smaller two-dollar notes)
b) Let’s imagine at first, Adam has 15 two-dollar notes like Brent, and he wants to be richer while keeping the same number of notes, he’d then changed 7 (=15-8) pieces of two-dollar notes into five dollar notes and he gets $3 richer for every piece of exchange. So he is 7x$3 =$21 richer than Brent.
Brent is $110 poorer than Clive because Brent spent 22 (=110/5) pieces of five-dollar notes. With that 15 pieces of two-dollar notes he has, Brent has a total number of 37 (=22+15) pieces of mixed notes. Likewise, Clive has 37 piece of all five-dollar notes. Sorry, corrected below. Pls see MathIzzzFun’s model or further explanation below. Thanks.