You always have to change the denominators (which are the bottom parts of the fraction) to be the same. To make it simple you do 8 as the denominators, 2 × 4= 8. Now all you have to do is add 2/8 + 3/8= 5/8 Easy as pie! Hope I helped you :)
You have to make the denominators the same so 1/4 and 3/8, times 1 and 4 by 2 so intead of 1/4 you have 2/8 and 2/8 + 3/8 which makes 5/8, which is a prime number so cannot be simplified