The random variable X is exponentially distributed, where X represents the waiting time to receive a custom ordered package from a company. If X has an average value of 15 days, what is the probability that the wait time is greater than 11 days

Idon't see any graph, however the graph of the function : f(x) = x²-2x+3 is a parabola: 1) open upward (since a> 0)2) it intersects y-axis in 3 (y=3)3) its axis of symmetry is x = +1 ( -b/2a)4) it's minimum is y = -2, so its vertex is (1,-2)5) it doesn't intersect the x-axis since discriminant < 0 

Difference means subtraction