If the 6th term of an arithmetic sequence is 12 and the 15th term is -15, find the first
term and the common difference.

7. the area of the playing surface at the olympic stadium in beijing isof a hectare. what area will it occupy on a plan drawn to a scaleof 1: 500?

Worth 30 points! in this diagram, both polygons are regular. what is the value, in degrees, of the sum of the measures of angles abc and abd?

An elevator travels 310 feet in 10 seconds. at that speed, how far can't his elevator travel in 12 seconds?