Final answer:
The total mass of the three coins is 3m units.
Step-by-step explanation:
In order to calculate the total mass, we need to add up the masses of all three coins.
The total mass of the three coins (mtot) can be found by simply adding the individual masses of each coin, given that each coin has a mass of m.
Since each coin has mass m, the total mass mtot of the three coins is given by:
mtot = m + m + m
Simplifying, we have:
mtot = 3m
Therefore, the total mass of the three coins is 3m units.