Please help me for geometry i totally forgot how to do it!

Two customers went to a post office. first customer paid $12 for 14 and 5 envelopes the second paid 24.80 for 10 postcards and 15 envelopes. what is cost of each envelope?

Average acceleration: i have no idea how to do this.

What are the solution(s) to the quadratic equation x2 – 25 = 0? o x = 5 and x = -5ox=25 and x = -25o x = 125 and x = -125o no real solution