Maria spent 36% of her savings to buy a smart phone. the phone cost $90. how much money was in maria's savings account before she purchased the phone? find the unknown value

$ 250

Step-by-step explanation:

let her savings be A

A/Q-

36% of A = $90

36/100 of A = $90

A = 90*100/36

A= $ 250

We have 10 ml of 20% acid to which we need to add "x" milliliters of 100% acid to make 50% acid.
 
.20 * 10 + 1.00x = .50 * (10 +x)
in which "x" is the volume of the 100% acid to be added.
2 + x = 5 + .5 x
.5x = 3
x = 6 milliliters

Source:
http://www.1728.org/mixture.htm
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