Answer:
addition because it's in parentheses and following PEMDAS parentheses comes first so you do addition first.
I hope you find this helpful :D
7/4 you do this because, for example you can think of it like pizza and pizza slices. You have 1 pizza and 3/4 of a pizza, let’s say each slice is 1/4 of a pizza. How many slices do you have altogether? Seven. You can also think of 1 as 4/4, so the just add 3/4 + 4/4 (which is technically just 3+4) = 7/4
There is nothing in the space. If there were, then the space would not be blank.