Question

Electric guitar kits originally cost $d$ dollars online. You buy the kits on sale for $50\%$ of the original price, plus a shipping fee of $\$4.50$ per kit. After painting and assembly, you sell each guitar online for $\left(1.5d+4.5\right)$ dollars. Find your profit on each guitar sold.

Answer 1

let's keep in mind that Profit = Revenue - Costs.

so each guitar costs originally "d" dollars online.

you buy the kits at half price, 50% of the original price, well, the original price is "d", half "d" is just 0.5d, and there's a shipping charge of $4.50. So the Cost to get one kit alone for you is 0.5d + 4.50.

After some work, you resell the kits online for 1.5d + 4.5, so since that's the selling price that is your Revenue for one kit.

`\stackrel{\textit{\Large Profit}}{\stackrel{Revenue}{(1.5d~~ + ~~4.50)}~~ - ~~\stackrel{Costs}{(0.5d~~ + ~~4.50)}}\implies 1.5d+4.5-0.5d-4.5 \\\\\\ 1.5d-0.5d+4.5-4.5\implies 1d\implies d`