Solve the following system of equations by substitution.
2x - y = 6
x + y = 6

The general form of the quetion of a circle is ax^2+by^2+cx+dy+e=0 where a=b=0 if the circle has a radius of three units and the center lies on the y axis which set of values of a, b, c, d, and e might correspond to the circle

Which equation results from adding the equations in this system? x+6y=9 and -x+2y=-15

Simplify the given expression leaving the answer in improper fraction form. 2/3+5/6