pls help me

Question

Mr lim went to the bookstore and found that 5 similer files cost $3 more than 3 similar pens.He purchased 3 files and 6 pens for $17.40.What is the cost of each file?

Answer 1

Let's let F = Cost of a File,  P = cost of a pen

 

Since 5 files cost $3 more than 3 pens we have:

5F = 3P +3

 

We also know that 3F + 6P = $17.40

 

We have two equations and two variables

 

5F = 3P +3               eqn 1

3F + 6P =17.4          eqn 2

 

5F-3P =3          by subtracting 3P from both sides of eqn 1

3F+6P=17.4

 

We need to eliminate one variable.  If we multiply the new eqn 1 by 2 we will have -6P and

when we add the equations together it will eliminate the P variable so we can solve for F

 

10F-6P=6      (eqn 1)(2)

3F +6P=17.4

__________

 

13F = 23.40

 

F = 23.40/13

 

F = $1.80

 

Each file costs $1.80