Question 211265
Katie has $880 in five- and twenty-dollar bills. If she has four more twenties than fives, how many 20-dollar bills does she have? 
------------------------
Let # of fives be "f"; Let # of twenties be "t".
Equations:
Value Eq: 5f + 20t = 880
Quantity Eq: t = f+4
--------------------------------
Substitute and solve for f and then for t.
=================================================
Cheers,
Stan H.