Ethan decided to give 10% of his monthly income to charity. This month, he wrote the calculation at right. Explain why this calculation is appropriate and finish it for him. How much money should he give this month?

The answer of this question is 672 .

I’m pretty sure the answer is a

Iam unsure about what the proof is, therefore as much as wish to i can not.

First locate the turning point (vertex) of the graph. which is at the coordinates x=5 and y=9 or (5; 9).to determine whether it's a maximum or mininum value, you have to discern whether the vertex's y-value is the highest value or lowest value the graph can reach. since the vertex's y-value, 9 is the highest value the graph can reach, it will be a maximum.another basic way to determine whether the vertex's value is max or min is to see if the graph is smiling or sad. if it's smiling, the turning point/vertex would be a minimum, while a sad parabola would have a maximum y-value at the vertex.