With a calculator, multiplication, division, addition, and subtraction operations are done in that priority/sequence.
So, in your expression, 'over' is handled first, then 'minus'.
The question becomes 'what is (4/6) minus (1/2)?'
4/6 - 1/2 = 4/6 - 3/6 = 1/6
2 minus 2/5 plus 1/2 minus 4 = -1.9
It is: 4/5 minus 1/2 = 3/10
-1/4
10/12 minus 2/4 is 1/3
-1/2 4/4= 1 1-2= -1 -1/2= negative one half
1/6
1/6
2/5 = 4/10 minus 1/10 is 3/10
3/6 minus 2/8 is 1/4
2 and 1/12 minus 1 and 1/3 = 3/4 or 0.75
1 1/4 minus 2/3 is 7/12
It is: 1/2