Explanation:
in case of doubt in % calculating always remember to determine what is 100% and what is 1%. and then multiply or divide as needed.
and because we are dealing with 100% to be the whole (1), percentages as part of the 100% can be also expressed as decimals.
e.g. 25% = 0.25
or to add 30% to a number x means multiplying x by 1.30 (1 whole plus 30%).
so, we have here
100% = $25
1% = 100%/100 = 25/100 = $0.25
therefore
8% = 8×1% = 8×0.25 = $2.00 = 100%×0.08 = 25×0.08
15% = 15×1% = 15×0.25 = $3.75 = 100%×0.15 = 25×0.15
so, she spent in total
$25 + $2 + $3.75 = 25×(1 + 0.08 + 0.15) = 25×1.23 =
= $30.75