He bought 19/24 pounds of grapes.
3 5
------- + ------- = 0
8 12
In adding fractions.
Step 1: make sure the denominators are the same. 8 and 12 are not the same. But both are factors of 24.
8 * 3 = 24
12 * 2 = 24
Multiply both numerator and denominator of 3/8 by 3 and 5/12 by 2.
3 * 3 5 * 2 9 10
--------- + ------------- = -------- + ---------
8 * 3 12 * 2 24 24
Step 2. Since the denominator is now the same, add the numerator and put it over the denominator.
9 + 10 19
---------- = -------
24 24
Step 3. Simplify the fraction.
19
----
24 is already the simplified form.
