Troy and Lisa were shopping for school supplies. Each purchased different quantities of the same notebook and thumb drive. Troy bought 12 notebooks and 4 thumb drives for $100. Lisa bought 3 notebooks and 15 thumb drives for $249. Find the cost of each notebook and each thumb drive.

Sarah,

Let x = cost of notebook

let y = cost of thumbdrive

For Troy   5x + 5y = 75

For Lisa    2x + 6y = 78

Troy's equation let's divide it by 5 and get

x+ y = 15     multiply by -2

-2x -2y  = -30

2x + 6y = 78    Add equations

      4y = 48

Solve for y.  Then plug it in one of the original equations and solve for x.  Check by plugging into the other original equations

Step-by-step explanation:

1 is to a because corresponding angles are located in the same location, comparative to each line.

2 is to d because one, they are on the same side of the transversal, and two, they are "facing" each other.

3 is to c because vertical angles are formed opposite to each other when two lines intersect, like shown.

4 is to b because they are on different sides of the transversal, and are "facing" each other.

5 is to e because they are not "facing" each other, and they are on different sides of the transversal.