How do I regroup this for associative property

5 + 6) + (4 + 7) + 3

Delbert keeps track of total of the total number of points he earns on homework assignments, each of which is worth 60 points. at the end of the semester he has 810 points. write an equation for delbert’s average homework score a in terms of the number of assignments n.

X^2/100+y^2/25=1 the length of the major axis is: a)5 b)10 c)20

Twice the sum of a number and 2 is equal to three times the difference of the number and 8. find the number.