Can I have some help please​

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

i do not have access to the graph, but from 2001 to 2011 the rate of unemployment in the united states changed drastically. it remained relatively steady, at 5 percent, on average (4.4 percent in 2006 due to the economic expansion and 6 percent in 2002 as a result of the elevated costs of the war of terror) until 2008. it was then when the financial crisis, the worst since the great depression of 1929, occurred. during the recession that followed, the unemployment rate reached almost 10 percent in 2009, and in 2010 it was above 9 percent. by 2011 job losses had been continuous and prolonged for months, but the rate decreased timidly.