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
The second graph I believe if not some else will try to help.
Your answer would be 13,122
You would multiply by -3 each time for this particular sequence.
Hope I helped!
1/25
think of it as 4/100
4 goes into 100 4 times
1/25+1/25+1/25+1/25=4/100