Answer:
30
Step-by-step explanation:
Let the amount of potting soil bought last week be

We know that this week's amount is 32 lb
We also know that this week's amount is double the amount of last week's plus 6 lb
So we write the equation:

Solving this equation:

⇒ subtracting 6 from both sides


⇒ Dividing both sides by 2


The answer is: 13
The distance from (-2,1) to (6,1) is 8 units
The distance from (6,1) to (6,-3) is 4 units
The distance from (6,-3) to (9,-3) is 3 units
Now add 'em up: 8 + 4 + 3 = 15
The length of the biking trail is 15 units long!
Hope that helps!