The weekly demand for DVDs in Suva is given as follows: Qd = 750 - 50P , where Qd represents the weekly demand and P is the price per DVD. What...

Though it may seem daunting if you're not used to working with demand curves, this question is very straightforward.

We are given that the weekly demand is Qd, the price is P, and the two are related by this equation:

Qd = 750 - 50 P

We are asked to find the weekly demand, so that's Qd. We are given that the price is $5. So all we need to do is substitute in $5 for P everywhere it appears in the equation. It only appears once, so that gives us:

Qd = 750 - 50 (5)

Now it's just arithmetic; remember your order of operations though. Multiplication occurs before addition. 50*5 = 250, so:

Qd = 750 - 250

Then, finally, 750 - 250 = 500, so

Qd = 500

The weekly demand at a price of $5 is 500 units.