Sarah's purse is full of $5 and $10 bills. She has 25 bills totaling $230. How many of each bill does she have?
+130555 Let x be the number of $5 bills and y be the number of $10 bills
And x + y = 25 (1)
And value of a five dollar bill * x + value of a ten dollar bill * y = total amount ......in other words.....
5x + 10y = 230 (2)
Rearranging (1), we have that y = 25 - x and putting this into (2), we have
5x + 10(25 - x) = 230 simplify
5x + 250 - 10x = 230
-5x + 250 = 230 subtract 250 from both sides
-5x = -20 divide both sides by -5
x = 4 this is the number of $5 bills she has
And y = 25 - x = 25 - 4 = 21 .....and this is the number of $10 bills she has
