Question

How many gallons of rocket fuel containing 80% liquid oxygen must be mixed with 250 gallons containing 40% liquid oxygen to produce a mixture containing 70% liquid oxygen?

Answer 1

Of course the canned answer by the "robot answer generator"
is wrong again.
Besides, just stating the answer without a solution is useless


number of gallons of 80% mixture to be added ---- x

.8x + .4(250) = .7(x + 250)
times 10
8x + 4(250) = 7(x + 250)
8x + 1000 = 7x + 1750
x = 750 <----- number of gallons of 80% mixture

Answer 2

wrong again, as usual.
80x + 40*250 = 70(x+250)
x=750

Answer 3

The answer is 500 gallons.