Three friends went to Staples for school supplies. Anna bought two notebooks, one pencil, and three binders for $14.50. Josh bought one notebook, four pencils, and one binder for $7.50. Alex bought 3 notebooks,
two pencils and two binders for $14.50. Find the price of each item by solving a system of three equations
algebraically

A pencil costs $0.50

A binder costs $3.00

A notebook costs $2.50

Step-by-step explanation:

Represent Notebook with N, Pencil with P and Binder with B

For Anna:.

2N + P + 3B = 14.50

For Josh:.

N + 4P + B = 7.50

For Alex:

3N + 2P + 2B = 14.50

Required

Solve for N, P and B

Make N the subject in the second equation

N + 4P + B = 7.50

N = 7.50 - 4P - B

Substitute 7.50 - 4P - B for N in the first equation

2N + P + 3B = 14.50

2(7.50 - 4P - B) + P + 3B = 14.50

Open Bracket

15.0 - 8P - 2B + P + 3B = 14.50

Collect like terms

3B - 2B + P - 8P = 14.50 - 15.0

B - 7P = -0.50

B = 7P - 0.50

Substitute 7.50 - 4P - B for N in the third equation

3N + 2P + 2B = 14.50

3(7.50 - 4P - B) + 2P + 2B = 14.50

22.50 - 12P - 3B + 2P + 2B = 14.50

Collect Like Terms

2P -12P + 2B - 3B = 14.50 - 22.50

-10P - B = -8

Multiply through by -1

10P + B = 8

Recall that B = 7P - 0.50

10P + B = 8 becomes

10P + 7P - 0.50 = 8

17P - 0.50 = 8

17P = 8 + 0.50

17P = 8.50

Divide through by 17

P = 8.50/17

P = 0.50

This implies that a pencil costs $0.50

Substitute 0.50 for P in B = 7P - 0.50

B = 7 * 0.50 - 0.50

B = 3.50 - 0.50

B = 3.00

This implies that a binder costs $3.00

Substitute 3.00 for B and 0.50 for P in N = 7.50 - 4P - B

N = 7.50 - 4 * 0.50 - 3.00

N = 7.50 - 2.00 - 3.00

B = 2.50

This implies that a notebook costs $2.50

there are infinitely many solutions.