SOLUTION: Which coins are in a piggy bank if all but 2 are nickels, all but 2 are dimes, and all but 2 are quarters?

Suppose there are n nickels, d dimes, and q quarters in the bank.

Then,

since all but two are nickels,

n+d+q-2=n 

or

d+q=2

since all but two are dimes,

n+d+q-2=d 

or

n+q=2

And since all but two are quarters,

n+d+q-2=q 

or

n+d=2

We have this system of three equations and 3 unknowns:



Solve that system and get n=1, d=1, and q=1.

So you have 1 of each.  You should have been able
to figure that out in your head, right?  :-)

Edwin