Posted by AJ on .
A bag contains forty coins, all of them either 2c or 5c coins. Let there be x 2c coins and y 5c coins. If the value of money in the bag is $1.55, find the number of each kind.

Math 
PsyDAG,
5x = 2y therefore
x = 2/5y
x + y = 155
Substitute 2/5y for x in last equation and solve for y. Insert that value into the first equation and solve for x. Check by inserting both values into the last equation.