3 1/2 - 3/4
Make the left side into an improper fraction like this
7/2 - 3/4
We want the bottoms to be the same, so multiply the top and bottom of the left side by 2
14/4 - 3/4
With the bottoms the same, now we can do this
(14 - 3) / 4
11 / 4
Can we reduce? 4 is just 2 * 2. 2 does not go into 11, so no, we can't reduce.
The answer is 11 / 4.