7 a lachat dun livre, la taxe est de 5 %. pour chaque livre, déterminez le montant de lachat avant taxes. a)…

Explanation:

Step1: Recall tax - amount formula

Let the pre - tax price be $x$ and the tax rate be $r$. The tax amount $T = x\times r$. We need to solve for $x$ when $T$ and $r$ are given, so $x=\frac{T}{r}$.

Step2: Solve part (a)

Given $T = 0.45$ and $r=0.05$ (since 5% = 0.05). Then $x=\frac{0.45}{0.05}=9$.

Step3: Solve part (b)

Given $T = 2.75$ and $r = 0.05$. Then $x=\frac{2.75}{0.05}=55$.

Step4: Solve part (c)

Given $T = 1.70$ and $r=0.05$. Then $x=\frac{1.70}{0.05}=34$.

Step5: Solve part (d)

Given $T = 36$ and $r = 0.15$ (since 15%=0.15). Then $x=\frac{36}{0.15}=240$.

Step6: Solve part (e)

Given $T = 45.60$ and $r = 0.15$. Then $x=\frac{45.60}{0.15}=304$.

Step7: Solve part (f)

Given $T = 50.40$ and $r = 0.15$. Then $x=\frac{50.40}{0.15}=336$.

Answer:

a) $9$ b) $55$ c) $34$ d) $240$ e) $304$ f) $336$