Two friends bought a couple of books at $33.42. They had $18.25 left after buying the books. How much money did they have before buying the books?

Question

Two friends bought a couple of books at $33.42. They had $18.25 left after buying the books. How much money did they have before buying the books?

Answer 1

Two ways to think about this: logic or algebra.

 

Logic

 

If we spend $10 and have $5 left, we would have started with $15. So we can just add the two numbers together.

33.42+18.25= 51.67

So they had $51.67 before buying the books.

 

Algebra

 

Assign a variable to what we want to know. We want to know how much money they started with. We will call that x.

$ start with = x

 

Now we put the words into an equation. They started with x. Then they spent 33.42. And that ended up with or equals 18.25.

x-33.42=18.25

Now we solve for x by adding 33.42 to both sides of the equation.

x=51.67

They started with $51.67.