step by step solve the equations

You should put parentheses around to avoid confusion!

6/(y+4)+1=5/(2y+8)

Notice that 2y+8=2*(y+4). Therefore, we can move 5/(2y+8) to the left, by changing its sign and writing it on the left with minus sign. We can also move 1 to the right, again, with sign change.

6/(y+4)-5/(2y+8)=-1; or 12/(2y+8)-5/(2y+8)=-1. Further transformation yields:

7/(2y+8)=-1 or 7=-(2y+8)

7=-2y-8 or 2y=-7-8=-15; y=-15/2=-7.5.