At the local pet store, Zebra fish cost $2.10 each and Neon Tetras cost $2.20 each. If Marsha bought 11 fish for a total cost of $23.50, not including tax, how many of each type of fish did she buy?

Answer 1

2.1Z + 2.2N = 23.5

Z + N = 11

multiply the 2nd equation by 2.1

2.1Z + 2.1N = 23.1, subtract result from the 1st equation to eliminate N

0.1N = 0.4 divide both sides by 0.1

N = 4 Neon Tetras

Z = 11-4 = 7 Zebra fish

Answer 2

x=# of zebra fish

y=# of neon tetras

x=11-y

2.1x+2.2y=23.5

2.1(11-y)+2.2y=23.5

23.1-2.1y+2.2y+23.5

.1y+23.1=23.5

.1y=.4

y=4

x=7

CHECK:

2.1*7= 14.70

2.2*4= 8.80

TOTAL 23.50