Question 807974
Amount of money remaining would be 200 dollars MINUS n*5 dollars.
This is {n CDS * 5 dollars/CDS}, or putting together the numbers separately from the units, {{{5n}}} {{{CDS(dollars/CDS)}}}.


The formula for amount remaining on the gift card is then {{{R(n)=200-5n}}}.


The second question only needs let n=10 and compute R(10).