algebra 1A

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

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  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.

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