Minimum price calculation

Question

I have 5 laptops. I'd like to find the price which I can use to sell these laptops and after applying the 20% tax the net amount must not be less than 7000$

Taking these variables into account please show the formula how to calculate this price.

Answer 1

Let the sales price be $x$. Then we find the desired sales price by solving $$x-0.20x=7000$$ This rearranges as $$0.8x=7000$$ Dividing both sides by $0.8$, we get $$x=\frac{7000}{0.8}=8750$$

Answer 2

Let $x$ be the price of one laptop. Then, what we want is:

$$5\cdot x - 0.2\cdot5\cdot x \geq 7000$$

Solving the inequation, we end up with:

$$x \geq 1750$$