At the local pet store, zebra fish cost $1.80 each and neon tetras cost $2.10 each. if ernesto bought 16 fish for a total cost of $30.90, not including tax, how many of each type of fish did he buy?

The number of each type of fish that Ernesto bought are 7 neon tetras and 9 zebra fishes.

Let the zebra fish be Z.Let the neon tetras be N.

Given the following data:

Total cost = $30.90Total number of fishes = 16 fishes.

To calculate the number of each type of fish that Ernesto bought:

How to solve a word problem.

First of all, we would assign a variable to each type of fish that Ernesto bought and then write a system of algebraic equations. Finally, we would solve the system of algebraic equations by using the substitution method.

Translating the word problem into an algebraic expression, we have;

   .....equation 1.

  .....equation 2.

From eqn. 1, we have:

     .....equation 3.

Substituting eqn. 3 into eqn. 2, we have:

N = 7 neon tetras.

For the zebra fish:

Z = 9 zebra fishes.

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The answer is k=-5

1 Expand - 3k - 21 - 5k + 4 = 23
2 Simplify - 3k - 21 - 5k + 4 to - 8k - 17 - 8k - 17 = 23
3 Add 17 to both sides - 8k = 23 + 17
4 Simplify 23 + 17 to 40. - 8k = 40
5 Divide both sides by . k = - 40/8
6 Simplify -40/8 to 5.

6 Simplify 40/8 to 5

k = - 5 Done