Why did manuel lisa follow the route of lewis and clark west?

Manuel Lisa was born in 1772 in New Orleans, Louisiana and died in 1820 in Missouri.

He was an important fur trader in the Mississippi area. Although he was of Spanish descent, in 1803,he became instant U.S citizen due to the Louisiana purchase.

Lisa followed the route of Lewis and Clark west because there were many stories about the presence of beavers in that area. As Lisa was very much interested in the beavers' fur he believed in those stories .

the us constitution is a living document, meaning that it can be changed over time as the country changes.

the perimeter of a triangle is 69 cm. side a is 5 cm shorter than side b. side c is twice as long as side a. find the length of each side. i need to know how to do it in 2 equations.  

equations:

a = b-5

c = 2a

a + b + c = 69