in this equation why does the 4 turn positive.

Question:

x/2-x-4/6=5/3

Solution:

x/2-x-4/6=5/3
3x-x+4/6=5/3
2x+4/6=5/3
3(2x+4)=6×5
6x+12=30
6x=30-12
6x=18
x=18/6=3​