I don't know how to set up this mixture word problem

Question

How many ounces of pure oil should be mixed with an oil gas solution that is 4.5% oil to get 100 ounces of an oil gas mixture of 15%.  I know I have to turn them into decimals

Answer 1

X ounces of pure oil

 

100 - x ounces of 4.5%

 

.045(100 - x) + 1(x) = .15(100)

 

multiply by 1000 to clear the decimal

 

45(100 - x) + 1000x = 150(100)

 

4500 - 45x + 1000x = 15000

 

                    955x = 10500

 

                         x = 10.99

 

mix 10.99 ounces of pure oil