Answer:
Small fish= 7
Big fish= 21/4 (so she'll get 5 big fish)
Explanation:
With the problem, there are two equations, one for the cost, and one for the amount of water. For the first equation, Alaina can spend 70 dollars and the fish cost 8 and 3 dollars so the equation is 70=8b+4s (s for small and b for big). Then for the second equation there are 14 available gallons and the fish require 2 and .5 gallons so 14=2b+0.5s. Then you just solve the system of equations.