ALGEBRA
posted by KIM .
A convention manager finds that she has $ 1410, made up of twenties and fifties. She has a total of 48 bills. How many fiftydollar bills does the manager have?

Let x = 50s and y = 20s
x + y = 48
x = 48  y
50x + 20y = 1410
Substitute 48  y for x in the second equation and solve for x. Put that value in the first equation to find y. Check by putting both values into the second equation.