Harriet has some five dollar bills and some one dollar bills She has 20 bills. The value of the bills is $72 write and solve a system of equations using elimination to find out how many of each bill she has.
Show your work please. should equal 7 one dollar bills and 13 five dollar bills. Also use ALGEBRA.
so let's say x=number of five dollare bills y=number of 1 dolar bills
20 bills total x+y=20
totla is 72 monies 72=5 times x+1 times y=5x+1y=5x+y solve
x+y=20 5x+y=72 from here you could do 2 things: go to option 1 (longer) or option 2 (shorter)
1.
x+y=20 subtract x from both sides y=20-x
5x+y=72 subtract 5x from boths ides y=72-5x subsitute
y=20-x=y=72-5x 20-x=72-5x add 5x to both sides 20+4x=72 subtract 20 from both sides 4x=52 divide both sides by 4 x=13
subsitute x+y=20 13+y=20 subtract 13 y=7
2.
another way is when you got 5x+y=72 and x+y=20 you negative the second equaiton and add to th efirst I know it sounds like voodo at first but it works -(x+y=20)=-x-y=-20 add
5x+y=72 -x-y=-20 + 4x+0y=52 4x=52 divide both sides by 4 x=13
