How many gallons of fuel costing 3.35 per gallon must be mixed with 20 gallons of fuel costing 3.85 per callonm to be obtain misrure costing 3.55?

30 gallons of fuel costing 3.35 per gallon must be mixed.

Explanation

Suppose,   gallons of fuel costing 3.35 per gallon must be mixed with 20 gallons of another fuel costing 3.85 per gallon.

So, the total amount of the mixture and the cost of the mixture is 3.55 per gallon.

So, the equation will be....

So, 30 gallons of fuel costing 3.35 per gallon must be mixed.