The common denominator for the numbers 4, 2 and 8 is 8.
This means we have to make 3/4 and 1/2 have the denominator of 8.
To get from 4 to 8 is to multiply by 2 and vice versa. This leads to 3/4 turning to 6/8 and 1/2 to 4/8.
The question now is...
6/8 + 4/8 - 5/8
If you calculate the question now it would equal to 5/8 because 6+4-5 equals 5.
