Question

What is the answer to 28 3/8- 19 5/6 and 18 2/5- 9 13/15

Answer 1

Each of the problems asks you to a similar idea: get a common denominator with  the fractions and then subtract.

Problem 1: 28 3/8 - 19 5/6

The factors of 8 are 2, 2, and 2. The factors of 6 are 2 and 3. We take one two that's repeated, two more twos from 8, and a 3 for the common denominator. So, 2 * 2 * 2 * 3 = 24 is the lowest common denominator (LCD).

Now  change the fractions to the common denominators

3/8 = ? / 24         We go from 8 to 24 multiplying by 3, so 3 multiplied by 3 is 9.

5/6 = ? / 24       We go from 6 to 24 multipling by 4, so 5 multiplied by 4 is 20.

Then,

28 3/8 - 19 5/6

= 28 9/24 - 19 20/24        <----use common denominators

= 27 33/24 - 19 20/24       <--- borrow from the whole number

= 8 13/24                           <---- subtract whole numbers and fraction numerators

Problem 2 works similarly to problem 1, with an LCD of 15.

18 2/5 - 9 13/15

= 18 6/15 - 9 13/15

= 17 21/15 - 9 13/15

= 8 8/15

Thus the differences are 8 13/24 (1st) and 8 8/15 (2nd).