Hank has a board 1.75 meters long. He used 0.8 meter to build the walls of a bird house. He used 0.4 of what is left for the floor. He needs 0.6 meter for the roof. Does he have enough wood for the roof?

Nope.

He doesn't have enough wood for the roof.

If you subtract 0.8 from 1.75: ##1.75-0.8 = 0.95##

Then you subtract 0.4 from 0.95: ##0.95-0.4 = 0.55##

There is not enough left for ##0.6m## for the roof.

You can't subtract 0.6, because if you do you'll get ##-0.05.##