Why gozzoli included portraits of the medici?

Painter Bennozzo Gozzoli created a series of painted mural portraits of the Medici family in the Magi Chapel located in the Palazzo Medici-Riccardi. Of these paintings includes the "Procession of the Three Kings" boasting both the large political and financial powers of the Medici family. Gozzoli strategically placed portraits of himself alongside the Medici family who were notable for ruling Florence, Italy.

c. as a force against soviet invasion of afghanistan

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