Looking at number 4, you first have to look at the information that you have:
On tuesday he practiced for 1 5/6 hrs
Monday he practiced for 7/10 hrs
He is supposed to practice for 1 1/4 hr.
You could write questions like:
How much more did Marco practice on Tuesday than he is supposed to practice?
This works because it does indeed involve subtraction, you would be subtracting the amount that he should have practiced from the amount of time that he did practice.
If I didn't answer the question, please message me and I will clarify!
The is answe is less than because I have to get them up
The solution (400, 3, 200) is the answer to a system of equations which has three variables. Respectively, this system is expected to have three equations because it has three unknowns. So for example if your unknowns are x, y and z, then the answers will be x=400, y=3, and z=200.
