Answer:
[tex]\$ 400[/tex].
Step-by-step explanation:
In this question, [tex]S[/tex] (sales price) and [tex]r[/tex] (discount rate) are both given. The unknown is the regular price, [tex]R[/tex].
Rearrange the discount equation to solve for [tex]R[/tex] in terms of [tex]S[/tex] and [tex]r[/tex].
[tex]S = R - r\, R[/tex].
[tex]S = (1 - r)\, R[/tex].
Divide both sides by [tex](1 - r)[/tex]:
[tex]\displaystyle \frac{S}{1 - r} = \frac{(1 - r)\, R}{1 - r}[/tex].
[tex]\begin{aligned}R &= \frac{S}{1 - r}\end{aligned}[/tex].
It is given that [tex]S = 320[/tex]. A mark-down of [tex]20\%[/tex] is equivalent to a discount rate of [tex]r = 20 / 100 = 0.20[/tex]. Substitute in [tex]S[/tex] and [tex]r[/tex] to find the value of [tex]R[/tex]:
[tex]\begin{aligned}R &= \frac{S}{1 - r} \\ &= \frac{320}{1 - 0.2} \\ &= \frac{320}{0.8} \\ &= 400\end{aligned}[/tex].
Thus, the regular price would be [tex]\$ 400[/tex].
