(a) Find

Find the lowest common denominator of 3 and 5
 

15 is the smallest number that divides both 3 and 5

the lowest common denominator is 15
 

Write both fractions as equivalent fractions over 15 (by multiplying top and bottom by the same amount)
 

 

Add the numerators and write over a single denominator
 

 

There is no cancellation

(b) Find giving your answer as a mixed number

Change the mixed number into a top heavy fraction (by multiplying the denominator, 4, by the whole number, 3, then adding the numerator, 3)
 

 

To find first find the lowest common denominator of 4 and 8
 

8 is the smallest number that divides both 4 and 8

the lowest common denominator is 8
 

Write both fractions as equivalent fractions over 8 (by multiplying top and bottom by the same amount)
 

 

Subtract the numerators and write over a single denominator
 

 

Change into a mixed number (by dividing 25 by 8 to get 3 remainder 1)
 

There is no more cancellation