The unknown number . . . . . (z)
The sum of the unknown number and 22 . . . . . (z + 22)
The sum of the unknown number and 22
divided by the same unknown number . . . . . . . (z + 22) / z
You said that quotient is 12. (z + 22) / z = 12
Multiply each side by 'z' : (z + 22) = 12 z
Subtract 'z' from each side: 22 = 11 z
Divide each side by 11 : 2 = z .
Answer: Choice B) 
Work Shown:

Note: secant is positive in quadrant Q4, when theta is between 3pi/2 radians and 2pi radians (270 degrees and 360 degrees). So that's why we don't consider the minus form of the plus minus.
Answer:
the domain of the function is all real numbers less than or equal to 0
Te difference of 2 standard deviation of a population n1 & n2 is given by the formula:
sigma (difference)=√(sigma1/n1 + sigma2/n2), Plug:
sigma(d)= √(49/100 + 36/50)
Sigma(d=difference) =1.1