If ~$\frac{s}{t}$~=2, then the value of which of the following can be determined?

I ~$\frac{2t}{s}$~

II ~$\frac{s-t}{t}$~

III ~$\frac{t-1}{s-1}$~

The sum of the ages of Doris and Fred is y years. If Doris is 12 years older than Fred, how many years old will Fred be y years from now, in terms of y?

If k≠0 and k- ~$\frac{3-2k^2}{k}$~ =~$\frac{x}{k}$~, then x=

Machines X and Y run at different constant rates, and machine X can complete a certain job in 9 hours. Machine X worked on the job alone for the first 3 hours and the two machine working together, then completed the job in 4 more hours. How many hours would it have taken machine Y, working alone, to complete the entire job?

If N= ~$\frac{K}{T+\frac{x}{y}}$~,where T=~$\frac{K}{5}$~and x=5-T, which of the following expresses y in terms of N and T?

A merchant paid $300 for a shipment of x identical calculators. The merchant used two of the calculators as demonstrators and sold each of the others for $5 more than the average(arithmetic mean) cost of the x calculators. If the total revenue from the sale of the calculators was $120 more than the cost of the shipment, how many calculators were in the shipment?

 If there is a least integer that satisfies the inequality ~$\frac{9}{x}$~ ≥2, what is that least integer?

A certain truck traveling at 55 miles per hour gets 4.5 miles per gallon of diesel fuel consumed. Traveling at 60 miles per hour, the truck gets only 3.5 miles per gallon. On a 500-mile trip, if the truck used a total of 120 gallons of diesel fuel and traveled part of the trip at 55 miles per hour and the rest at 60 miles per hour, how many miles did it travel at 55 miles per hour?

On the day of the performance of a certain play each ticket that regularly sells for less than $10.00 is sold for half price plus $0.50, and each ticket that regularl sells for $10.00 or more is sold for half price plus $1.00. On the day of the performance, a person purchases a total of y tickets, of which x regularly sell for $9.00 each and the rest regularly sell for $12.00 each. What is the amount paid, in dollars for the y tickets?

In the formula w=~$\frac{P}{\sqrt[t]{V}}$~，integers P and t are positive constants.If w=2 when v=1 and if w=1/2 when v=64, then t=