What are the different geographical farmers work of world in past

Explanation:

Arable Farming. Arable farming involves growing of crops only in warm climate.

Pastoral Farming. Pastoral farming is the practice of rearing animals only in cold and wet climates not ideal for growing crops.

Mixed Farming. Mixed farming involves growing of crops and rearing of animals on the same piece of land.

Subsistence Farming. Subsistence farming is the practice of growing crops and rearing animals for personal use.

Commercial Farming. Commercial farming is practiced for the purpose of making a profit.

Extensive and Intensive Farming. Extensive farming or cultivation involves land tillage with an aim of increasing output

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