Explain what kind of art was being created during(New Stone Age)

Weaving, architecture, megaliths, and more sophisticated pictographs that were well on their way to becoming writing were among the "new" arts that emerged during this period. The older arts of sculpture, painting, and ceramics have stayed with us (and continue to do so). Each was greatly refined throughout the Neolithic age.

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

sorry i cant