It’s 81 and an exponential fraction saying 3/4 on top of the 81 how do I simplify that?

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

Mrs. gehrke said cheddar weighs 16.8 pounds. he actually weighs 15.2 pounds. what is the percent error?