if you see fractions, and the question says "same amount", that means its an equal fraction concept
step 1: find the equal fraction
"In the end, Dexter and Brad had the same amount of money left."
dexter left (fraction) → 1 - 5/6 = 1/6
Brad left (fraction) → 1 - 3/5 = 2/5
1/6 Dexter = 2/5 Brad
step 2: make numerators the same
2/12 Dexter = 2/5 Brad
step 3: convert denominators to total units
dexter total → 12u brad total → 5u
step 4: solve
" Dexter had $210 more than Brad at first."
difference → $210 difference (units) → 12 - 5 = 7u
7u → 210 1u → 210 ÷ 7 = 30 5u (Brad at first) → 5 x 30 = $150