My math problem is this: solve the following system of equations.
5x-4y=24
-2x+7y=12
I have tried and I can not figure it out. I have to try and find out what x&y are.​

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?

Anumber cube is rolled two times in a row. find the probability it will land on 2 on the first roll and a number greater then 4 on the second roll

Among the most famous of all meteor showers are the perseids, which occur each year in early august. in some areas the frequency of visible perseids can be as high as 40 per hour. given that such sightings are poisson events, calculate the probability that an observer who has just seen a meteor will have to wait at least five minutes before seeing another.