Answer:
The probability that a call last between 4.2 and 4.9 minutes is 0.4599
Step-by-step explanation:
Let X be the length in minutes of a random phone call. X is a normal distribution with mean λ=4.2 and standard deviation σ=0.4. We want to know P(4.2 < X < 4.9). In order to make computations, we will use W, the standarization of X, given by the following formula

We will use
, the cummulative distribution function of W. The values of
are well known and the can be found in the attached file

We conclude that the probability that a call last between 4.2 and 4.9 minutes is 0.4599
Answer:
-2<x≤5
Step-by-step :
-1<x+1≤6 So fisrt what every we do to one side we must do to the other. In this case it's a bit different since we are dealing with inequalities.
-1<x+1≤6 I would start off by isolating x in the middle.
-1<x+1≤6 I subtracted 1 from all three sides.
-1 -1 -1
Now your equation should look like this:
-2<x≤5 Now there is really nothing much we can do here since we were just trying to get x by its self.
Answer : -2<x≤5
7% = 0.07
0.07/4 = 0.0175
The answer is 0.0175