Question

at the local per store, zebra fish cost $2.10 each and neon tetras cost $1.80 each. if marsha bought 13 fish for a total of $25.80, not including tax, how many of each type of fish did she buy?

a)7 zebra, 6 neon
b)8 zebra, 5 neon
c)6 zebra, 7 neon
d)5 zebra, 8 neon

Answer 1

X Zebra fish.
Y Neon fish.

Eq1: X + Y = 13.
Eq2: 2.1X + 1.8y = 25.80
Multiply Eq1 by -2.1:
-2.1x - 2.1y = -27.3
2.1x + 1.8y = 25.8
Add the Eqs:
-0.3y = -1.5
Y = -1.5 / -0.3 = 5 = Neon.
X + 5 = 13
X = 8 Zebras.