Answer:
You would need 5 gallons of a 70% solution
Step-by-step explanation:
You can always use proportions to answer these types of questions.
The numerator will be the amount of acid and the denominator will be the amount of solution
30% of 3 gallons is 0.9.
[tex]\frac{0.9+\frac{7G}{10} }{3+G} =.55\\0.9 + .7G = 1.65 + .55G\\.15G = .75\\G=5[/tex]