Ajar contains n nickels and d dimes. there are 26 coins in a jar, and the total value of the coins is $2.00. how many nickels and how many dimes are in the jar?

So you want to make 2 equations like this:
n+d=26
0.05n+0.10d=2
Now, use substitution and get d=26-n
plug that into the next equation and get

0.05n+0.10(26-n)=2
Distribute and combine like terms
0.05n+2.6-0.10n=2
2.6-0.05n=2
subtract 2.6 from both sides and you get 

-0.05n=-0.6
Solve for n by dividing and you get
12 nickels.
Now, plug that into the first equation and you get
12+d=26
d=14

14 Dimes and 12 Nickels

Hope this helped!

The second and fourth answer are correct