Why are the equations w - x + x = w and w + x - x = w called identities?

The line containing the midpoints of the legs of right triangle abc where a(-5,5), b(1, 1), and c(3, 4) are the vertices.

Ijust need to see how to do this. so you don’t have to answer all of them just a step by step explanation of one.

You were told that the amount of time lapsed between consecutive trades on the new york stock exchange followed a normal distribution with a mean of 15 seconds. you were also told that the probability that the time lapsed between two consecutive trades to fall between 16 to 17 seconds was 13%. the probability that the time lapsed between two consecutive trades would fall below 13 seconds was 7%. what is the probability that the time lapsed between two consecutive trades will be between 14 and 15 seconds?