Andrew M. answered • 06/26/15

Tutor

New to Wyzant
Mathematics - Algebra a Specialty / F.I.T. Grad - B.S. w/Honors

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