How do you get the square root of 144

Ben is three times as old as samantha, who is two years older than half of michel's age. if michel is 12. how old is ben?

How do you use the elimination method for this question? explain, because i really want to understand!

Asquare has a side that measures 11 units. what is the area of a circle with a circumference that equals the perimeter of the square? use 3.14 for π, and round your answer to the nearest hundredth. 1519.76 units2 379.94 units2 616.56 units2 154.14 units2