I don't understand 6y - (2y-5) = 29

So,

6y - (2y - 5) = 29

Distribute.

6y - 2y + 5 = 29

Collect Like Terms.

4y + 5 = 29

Subtract 5 from both sides.

4y = 24

Divide both sides by 4.

y = 6

Check.

6 (6) - (2 (6) - 5) = 29

6 (6) - (12 - 5) = 29

6 (6) - (7) = 29

6 (6) - 7 = 29

36 - 7 = 29

29 = 29 This checks.

S = {6}