What is the last one number 12
Answer:

Step-by-step explanation:
let a be the number of tennis balls.
let b be the number of tennis rackets.
We write determine the ratio of balls to rackets by dividing the number of balls by the number of rackets:

For every one ball, there 5 thirds of a racket.
We plot this function on a graph to visualize our model;
Answer:
The vertex is (-3, 7)
Step-by-step explanation:
As the equation is already in 'rectangular form), to work out the vertex, we can just compare this equation to that of the standard parabola y = x^2, and in particular, consider how it has been translated:
the (x+3) part moves the graph the the left 3 (i.e in the negative direction), while the +7 moves the graph up 7.
So as the vertex of the simple parabola y = x^2 is (0,0), the vertex of this graph is just (-3,7).
Note that the -2 at the front doesn't impact this vertex - this -2 just changes the 'scale' of the parabola (i.e makes it more narrow, and also turns it upside down as it's a negative number).
Answer:
2r - 15
Step-by-step explanation:
product of 2 and r is 2r and then minus by 15. im sorry if this is wrong haha