Answer:
.4!
Step-by-step explanation:
first you divide 20 by 125 and get .16
then you take the square root of .16 and get .4
5 DVDs would cost 7.50 and the unit rate is 3.50
The mistake was when she multiplied the 2nd equation by 5, she forgot to also multiply that last number 10 by 5 as well.
correction :
5x + 3y - z = 15
-x + 2y + 3z = 10...multiply by 5
---------------------
5x + 3y - z = 15
-5x + 10y + 15z = 50 (result of multiplying by 5)
--------------------add
13y + 14z = 65
