Translate to a system of equations and solve - linear systems

Question

Troy and Lisa were shopping for school supplies. Each purchased different quantities of the same notebook and thumb drive. Troy bought four notebooks and five thumb drives for $124. Lisa bought two notebooks and three thumb dives for $72. Find the cost, in dollars, of each notebook and each thumb drive.

Answer 1

Let N = cost of notebooks and T = cost of thumb drives

Troy: 4N + 5T = 124

Lisa: 2N + 3T = 72

Multiply Lisa's equation by 2

4N + 6T = 144

Subtract Troy's equation from this one

T = 20

From Troy's equation: 4N + 100 = 124

4N = 24

N = 6

Answer 2

4n + 5t = 124

2n + 3t = 72

Multiplies second equation by -2

4n + 5t = 124

-4n + -6t = -144

Adds them together

-t = -20

t=20

Substitutes into first equation:

4n + 5(20) = 124

4n + 100 = 124

4n = 24

n = 6

notebook cost $6 and thump drive costs $20