In the question it is already given that Eric drove for 439.92 miles on 15.6 gallons. It is required to find the distance traveled on 39.7 gallons of gas. Also we have to find the answer to the nearest hundredth.
Then,
In 15.6 gallons Eric can drive for a distance = 439.92 miles
In 39.7 gallons Eric can drive for a distance = [(439.92/15.6) * 39.7] miles
= 1119.54 miles
So the total distance traveled by Eric is 1120 miles with 39.7 gallons of gas. The answer has been calculated to the nearest hundredth.
The speed of the current is 40.34 mph approximately.
<u>SOLUTION:
</u>
Given, a man can drive a motorboat 70 miles down the Colorado River in the same amount of time that he can drive 40 miles upstream.
We have to find the speed of the current if the speed of the boat is 11 mph in still water. Now, let the speed of river be a mph. Then, speed of boat in upstream will be a-11 mph and speed in downstream will be a+11 mph.
And, we know that, 

We are given that, time taken for both are same. So 

If you want x, rearrange <span>Z=y+mx as follows: mx = z - y. Then div. all 3 terms by m:
z-y
x = ------- (answer).
m </span>
Hello from MrBillDoesMath!
Answer:
x = 19, y = 36
Discussion:
x + 3 = 22 (*)
2x - y = 2 (**)
Subtract 3 from both sides of (*)
x + 3 -3 = 22 = 3 = 19 =>
x = 19
Substitute x= 19 in (**)
2(19) - y = 2 =>
38 - y = 2 => (add y to both sides)
38 -y + y = 2 + y =>
38 = 2 + y => (subtract 2 from both sides)
38 -2 = 2 -2 + y =>
36 = y
Regards,
MrB
P.S. I'll be on vacation from Friday, Dec 22 to Jan 2, 2019. Have a Great New Year!