## Algebra 2 (1st Edition)

The number of rainbow fish bought is: $25-x-y$. Then the amount spent is: $f(x,y)=x\cdot1.5+y\cdot2+(25-x-y)\cdot8=1.5x+2x+200-8x-8y=200-6.5x-6y$. Thus if we buy 8 danios, 10 tetras, and rainbow fish, the cost is: $f(8,10)=200-6.5\cdot8-6\cdot10=200-52-60=88$