Answer:
Step-by-step explanation:

3 tons would be greater than 3,000 pounds
1 ton= 2,000 pounds
3 tons=6,000 pounds
644 is 80% of the regular price, so price=644/0.8 = 805 $
You must travel at 42 mph for 4 hours
<em><u>Solution:</u></em>
Time varies inversely as rate of motion
Let "t" be the time required
Let "r" be the rate of motion
Then, we get

Where, "k" is the constant of proportionality
<em><u>You travel 3 hours at a rate of 56 mph</u></em>
Substitute t = 3 and r = 56 in eqn 1

<em><u>Find the rate you must travel for 4 hours</u></em>
r = ? and t = 4
Substitute t = 4 and k = 168 in eqn 1

Thus you must travel at 42 mph for 4 hours