Gradient and y intercept coordinates of x=6+2y

Janets dinner costs 7.50. if she wants to leave a 10% tip how mich extra should she leave

Idon’t understand this.. will someone ? will mark brainliest along with 20 points.

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