How did the soviet union come to dominate eastern europe after world war 2

The Soviet Union enforced great power and influence over Eastern Europe during the years after World War. This was due to the spread of Communism among these countries, which led to the arrival to power of numerous communist regimes throughout Eastern Europe. This influenced was formalized with the Warsaw Pact of 1955, which established an intergovernmental organization of the Soviet Union with 7 other Soviet Satellite States. This organization was created as a response to the confirmation of the Western Powers's organization called NATO.

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