Question

Five pens cost as much as two notebooks. If the cost of one notebook and one pen is $1.75, what is the cost, in dollars, of one notebook?

Answer 1

Ok so for this problem we are going to make 2 equations.

Answer 2

The first one: 1.75 = x + y
The second on: 5x = 2y

Let x = cost of a pen
Let y = cost of a notebook

Do you understand how we got these?

Answer 3

yes I got it so far :)

Answer 4

Ok great, so there are a lot of problems like this. You have to make two equations with variables x and y. And we can manipulate one equation, set it equation to x or y. Then substitute that in the other equation and get the value of one variable. I'll show you what I mean by example:

Answer 5

5x = 2y
This is the same as

Answer 6

Watch this: i got this from the equation 5x = 2y.

This means that I have to substitute this into the OTHER equation. Don't subsittue this into 5x = 2y or else you will get 2y = 2y (And that's just an identity).

Answer 7

Ok so we substitue and we get: