Nick has 40 coins in his collection, all of which are either

Given the information, Nick has two kinds of coin: dimes, which we will label X, and nickels, which we will label Y. The total number of coins he has is 40, so
X + Y = 40.

Additionally, given the total value of his coins, we can multiple X by .1 (10 cents) and multiple Y by .05 (5 cents), and add these together to get 3.15
.1X + .05Y = 3.15

This gives us a solvable set of equations. Solve for one variable in the first equation, then replace that variable in the second.

Okay that brick wall and floor is identical to the outside my old high school cafeteria...I wouldn't be surprised if it was....

File: 1321288136382.jpg (149KB, 600x600px) Image search: [Google]

149KB, 600x600px

to solve you need to use the total number of coins, the values of the two coins, and the total value of those coins

number of coins: x+(40-x)
where x is 5 cent coins
values of the coins: 0.05x and 0.1(40-x) respectively

The total value 0.05x+0.1(40-x)=3.15
you should be able to solve it after this

>>166062
you don't need more than one variable

>>166065
What you've just posted is literally the next step in solving the set of two equations. If OP doesn't even know how to set up the beginning of the process, then skipping steps surely won't help.

>>166066
but there's only one equation
and i think it's hard if you don't know the victory conditions

>>166061

go to wolfram alpha
type in:
x+y=40,.1*x+.05y=3.15
profit.