What equation represents the nth term of the sequence {2, -1, -4, -7, ...} PLEASE HELP M

Someone this asap for a group of students attends a basketball game. * the group buys x hot dogs at the concession stand for $2 each. * the group buys y drinks at the concession stand for $3 each. the group buys 29 items at the concession stand for a total of $70. how many hot dogs did the group buy?

With both problems. a.s.a.p directions on photo ^

If the average of x,y and z is 15 what is their sum