George needs to make 8 gallons of tropical trip punch and the ingredients are pineapple juice, orange juice, and 7-Up.
He has 1 3/4 gallons of pineapple juice
and 2 1/2 gallons of orange juice.
To determine how much he needs of 7-Up, the first step will be to add the gallons of pineapple juice and orange juice that he already has.
Step 1. We add:

To add these fractions, we add separately the whole numbers and the fractions:

Since 1+2 is 3:

And, to add the fractions, we use the following formula:

Applying this to the sum we have:

solving the operations:


And we simplify 10/8 first as 5/4:

and now we simplify 5/4 as 1 1/4:

to complete the sum, we add 3+1 and get:

Step 2: From step 1 we know that he already has 4 1/4 gallons, and he needs to complete with 7-Up the 8 gallons.
So now, to find the amount of 7-up that he needs, we subtract 4 1/4 to 8:

To make this subtraction, it will be useful to have both numbers as a fraction:

and

So the subtraction we have to make is:

Since both fractions have the same denominator, we just subtract the numerators:

And finally, we simplify 15/4 to 3 3/4:
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