Help, need answers to test.

Equation for the calculation double 2 and then add 5

Using elimination, what is -4x+2y=-12 4x+8y=-24

Monitors manufactured by tsi electronics have life spans that have a normal distribution with a standard deviation of 1800 hours and a mean life span of 20,000 hours. if a monitor is selected at random, find the probability that the life span of the monitor will be more than 17,659 hours. round your answer to four decimal places.