Dan had to complete the remaining 1/3 of his science project this week. On Monday, he completed 4/5 of the work he had left to do. What part of the entire project did Dan complete on Monday?

Can you guide me on how to figure it out?

The common denominator of 1/3 and 4/5 is 15

So 1/3 of project or 5/15 is remaining
On Monday Dan completed 4/5 of remaining or 4/15 of entire project.
I think of it this way, if there are 15 pieces to complete
As of Monday 10 pieces were already complete which left 5
If Dan completed 4 out of the 5 then he completed 4 out of 15 which is the entire project.