What is this alcohol mixture problem asking?

How much 90 per cent alcohol must be added to 20 gallons of mixture which is 82 per cent alcohol to make the mixture 85 per cent alcohol?

I've tried using (.82)(20)+.9x=.85(20+.9x), but this doesn't yield an answer to the question.
Can anyone tell me how to start?

Thanks again

memorial said:

I've tried using (.82)(20)+.9x=.85(20+.9x)

Click to expand...

(.82)(20) + .9x = .85(20 + x) : you were close!

You can do it this way too (sometimes less confusing to remove decimals):
(82)(20) + 90x = 85(20 + x)

PS: wish you'd change your "name"; reminds me of a funeral :shock: