Write <em>z</em> in exponential form:

Then taking the logarithm, we get

so a is the correct answer.
The line underneath the inequality line(arrow) means p is less than OR EQUAL to 21.
An example off the top of my head would be, Rachel just started a new job that pays 7 dollars per hour. She only worked 3 hours and decided she wanted to go to the mall to buy some clothes. How much money does Rachel have to spend?
And your answer is right there
Step-by-step explanation:
The domain is the possible x values of a function.
Since our function is a reciprocal function, our denominator can't equal 0. Note x=0, is a vertical asymptote.
So our domain is
All Reals except 0,
or (-oo,0) U (0, oo).
Because it's decreasing, you use the formula (1-x/100)y with x the percentage decreased which is here 40, and y the number decreased which is here 90
So we get
(1-40/100) * 90
(100/100 - 40/100) * 90
60/100 * 90
5400/100
54
So 90 decreased by 40% is 54
Hope this Helps :)