Prectange caculation math please help

Question

I have 200 grams which is 67% pure

If i had to make those 200 grams 10% pure by only using 1.8% pure same chemical how much would i need and how many grams would it weight after it ?

Answer 1

.67(200) +.018x = .1(200+x)

134+.018x =20 +.1x

(.1-.018)x =134-20

.0982x = 114

x =114/.0982 = 1160.9 g of 1.8% to get 1360.9 g 10%

134+2.09 =136.09