Lets simplify
please help step by step

Negative 5 1/12 + negative 4 1/4 + 6 3/4

Which coefficient matrix represents a system of linear equations that has a unique solution ? options in photo*

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.