The answer is 19/20 Gallon
Step-by-step explanation:
So, to get the correct answer, you need to find a common denominator to be able to add the numerator and the denominator(3/4) with the other fraction(1/5).
To find the common denominator, you have to find the first number they are both equal to, which in this case, the first one is 20, so you would change both denominators in the fractions to 20.
The first fraction, 3/4, you have to multiply the 4 with the number 5 to get the answer 20, and whatever you do to the denominator you have to do with the numerator. So you would multiply 3 by 5, just as you did with 4 and get the answer of 15. So the first fraction is 15/20.
The second fraction, 1/5, you have to multiply 5 with the number 4 to get the same denominator as the first fraction, 15/20. And 5 x 4= 20, so you would change the second fraction's denominator to 20, and as I've said before: Whatever you do to the denominator, you have to do to the numerator. So you would multiply the second fraction's numerator by 4. So 1x4= 4, which makes the fraction 4/20.
So now, since you've made the denominators the same, you will have to add the numerators together: In the first fraction, 15 is your numerator while in the second fraction, 4 is your numerator. 15+4= 19.
After you add the numerators to get the answer of 19, you do not add or do anything with the denominators, they stay the same. Making the answer 19/20.