GAC: Sharon has some one-dollar bills and some five-dollar bills. She has 14 bills. The value of the bills is $30. Solve a system of equations using elimination to find how many of each kind of bill she has.
"x" number of one dollar bills
"y" number of five dollar bills
She has 14 bills:
x+y=14
The value of the bills is $30:
x*1$ + y*5$ = 30$
x + 5y = 30
so that's two equations for two unknowns (x,y):
x + 5y = 30 and x+y=14
Solve:
x+y=14 equals x=14-y
insert this for "x" into the other equation:
(14-y) + 5y = 30
14-y + 5y = 30
14 + 4y = 30
4y = 30-14
4y = 16
y = 16/4
y = 4 , so that's 4 times a 5 dollar bill
insert y into second equation:
x=14-y
x=14-4
x=10 , so that's 10 times a 1 dollar bill
test:
10*1 + 4*5 = 30 (check)
[input]x+5y=30, x+y=14[/input]
+3146 
