When the boat headed 21 miles north then 28 miles to the east then back to its starting point, it formed a right angle triangle. And that straight line the question is talking about is the hypotenuse.
Use the Pythagorean Theorem to solve for hypotenuse.
The Pythagorean Theorem states that for any right triangle the following is true: when you take the sum of both of the legs squared it will equal to the hypotenuse squared.
In equation form:

Where the variables a and b are the legs. And the variable c is the hypotenuse.
Plug in the values.



35 = c
So, the straight line is 35 miles long.
<span>The value of z is 0.8770. This answer was derived from information in the question, which states that the value of z is 0.8770. Granted, I don't understand what is meant by "cumulative standardized normal distribution." I only passed statistics because the professor felt sorry for me.</span>
Part a : you could draw a line from each corner to the middle
This would give you 7 triangles in total
Part b : area of one triangle : 4.5*7.8 = 35.1 / 2 = 17.55in <-- area of 1 triangle
Part c : so if there are 7 triangles and the area of 1 triangle is 17.55, you would do:
7 * 17.55 = 122.85
Subtracting 10x from the given equation gives
120 = 15x
Then dividing by 15 gives
8 = x
Zorah will have to play 8 hours in order to break even (cover her expenses exactly).