If you're adding positive numbers together, then the order in which you write or group the addends doesn't matter.
If you're "adding" a negative number to a positive number, it's a little easier to visualize this problem if you write the positive number first, followed by the negative number.
But if you're "adding" -15 to 8, it'd make sense to write the -15 first (because its magnitude is greater) and then the 8: -15 + 8 = -7
C because you have to divide by m or the members because you are splitting it up or dividing it between the members. And you subtract 95 dollars becuase it was a cost or bill
