Answer:
t = 0.293 s and 14.52 s
Step-by-step explanation:
The heights of the ball in feet is given by the equation as follows :

Where t is the number of seconds after the ball was thrown.
We need to find is the ball 18 ft above the moon's surface.
Put S = 18 ft

It is a quadratic equation. Its solution is given by :

So, the ball is at first 0.293 s and then 14.52 s above the Moon's surface.
You need to find the amount subject to withholding, subtracting from the weekly salary the amount for one withholding allowance for weekly salaries, which is 77.90$:
830 - 77.90 = 752.1 $.
Then, look in the Fed Tax tables (
http://www.opers.ok.gov/Websites/opers/images/pdfs/2016-Fed-Tax-Tables.pdf ) for a married person with a weekly payroll.
You previously found an amount of 752.1 which is greater than 521 but less than 1613$: therefore the income tax to withhold is 35.70$ + 15% of excess over $521.
Therefore, calculate the income tax due: 35.70 + (752.1 - 521) × 15 ÷ 100 = 70.37$
The total amount of income tax that will be withheld is 70.37$