It's i ready and i'm bad at math

If f(x)=3x+1 and f^-1=x-1/3, then f^-1(7)=

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?

What are the values of a, b, and c in the quadratic equation 0 = x2 – 3x - 2? a = 1, b = 3, c = 2 a=, b = -3,c=-2 a = 1, b = 3, c= 2 a = 1.0= -3, c = 2