Doreen schmidt is a chemist. she needs to prepare 36 ounces of a 10% shydrochloric acid solution. find the amount of 18% solution and the amount of 9% solution she should mix to get this solution

Total = 36oz
Amount of 18% solution = x
Amount of 9% solution = 36 - x

Using the fact that (amount of solution) * (percent HCl) = amount HCl we can set up an expression for the amount HCl in a mixture of 18% and 9% solutions with a total volume of 36oz.

Amount of HCl = x*0.18 + (36 - x)*0.09

If we divide this by the amount of solution we get percent HCl, and we have a target of 10% HCl. Now we have an equation to solve,

[x*0.18 + (36 - x)*0.09]/36 = 0.1

x*0.09 + 3.24 = 3.6

.09x = 0.36
x = 4

Therefore,
4 ounces of 18% HCl solution and 32 ounces of 9% HCl solution

Check:
[(4*.18) + (.09*32)]/36 = 0.1?
0.1 = 0.1   Yes.

Ican't solve. your equation is impossible. you can't have two equal signs.