Helppp what’s the answer to this question

What is the value of  y  in the solution to the system of equations? x  +  y  =  12x  –  3y  =  –30a. –8b. –3c. 3d. 8

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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?