Arrange the following numbers in increasing order: \begin{align*} A &= \frac{2^{1/2}}{4^{1/6}}\\ B &= \sqrt[12]{128}\vph
antom{dfrac{2}{2}}\\ C &= \left( \frac{1}{8^{1/5}} \right)^2\\ D &= \sqrt{\frac{4^{-1}}{2^{-1} \cdot 8^{-1}}}\\ E &= \sqrt[3]{2^{1/2} \cdot 4^{-1/4}}.\vphantom{dfrac{2}{2}} \end{align*}Enter the letters, separated by commas. For example, if you think that $D < A < E < C < B$, then enter "D,A,E,C,B", without the quotation marks.
So first create and define your variables: Z = amount of zebra fish N = amount of neon tetras
Now create your equations: 2z+2.15n=31.20 z+n=15 This is your system. There are multiple methods to use but in this problem I’ll use the substitution method by simplifying the bottom equation. 2z+2.15n=31.20 z=15-n Now I’ll plug the bottom equation into the top one. 2(15-n)+2.15n=31.20 And just solve from here. 30-2n+2.15n=31.20 0.15n=1.20 n=8 So he bout 8 neon tetras, and 15-8= 7, so he bought 7 zebra fish