8 and 3 both have a lowest common multiple of 24. to get 8 to 24 you multiply by 3, to get 6 to 24 you multiply by 4
So to do any addition or a subtraction easily you would need to multiply by their respective numbers, both the top and bottom, 5*3/8*3 = 15/24 , 3*4/6*4 = 12/24
from here all you have to do is subtract a negative number which is the same as add the positive version
15/24 + 12/24 = 27/24 = 1+3/24
3 goes into 24 8 times so 3/24 = 1/8
So your answer can be 1+1/8 or 9/8
