Question

At the local pet store, zebrafish cost $2.15 each, and neon tetras cost $2.30 each. If Ernesto bought 13 fish for a total cost of $28.55, not including tax, how many of each type of fish did he buy?

Answer 1

Answer:

9 zebra fish, 4 neon tetras

Step-by-step explanation:

Let t represent the number of tetras and z represent the number of zebra fish.

The total number of fish Ernesto bought is represented by t + z = 13 and the total cost of Ernesto's fish purchase is represented by 2.30t + 2.15z = 28.55.

To find out how many of each type of fish Ernesto bought multiply the first equation by 2.15 and then write the system of equations so that the equations are aligned in order to subtract the second equation from the first:

2.15t + 2.15z = 27.95

−(2.30t + 2.15z = 28.55)

−0.15t = −0.6

Solve for t:

t = 4

Substitute t = 4 into one of the original equations and solve for t:

4 + z = 13

z = 9

Ernesto bought 9 zebra fish and 4 neon tetras.