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
