How do you subtract positive and negative integers

Which expression will have the same sum as 3_8 + 1/4?

How do i start to solve? would appreciate a walk-thru! a bird sitting 16ft above the ground in an apple tree dislodges an apple. after how many seconds does the apple land on the ground? (assuming that no branches will interfere with it's fall)

According to the general equation for conditional probability if p(anb)=3/7 and p(b)=7/8 what is p(a i b)