The answer is the sixth grade class.
In order to find the answer, you have to divide each grade's total by the number of hours it took them to make that money, which will give you the amount each class makes per hour.
$170 / 55 = $3.09
$112 / 44 = $2.54
$192 / 66 = $2.91
The given expression is

And since we have x+2 common in numerator and denominator, there is a hole at x+2=0, that is at x=-2
And a function is undefined when denominator is zero. And at x=-6, denominator become zero.
So, at x=-6, the function is undefined, or there is a vertical asymptote at x=-6 and hole at x=-2 .
The problem here is: Too many words.
If you boil the problem down to the bare facts, the question is:
"$210 is 15% of what number ?"
I'm pretty sure you can take it from there,
but here's the rest of it anyway:
$210 = 15% of (March amount)
$210 = 0.15 x (March amount)
Divide each side by 0.15 : $1400 = March amount .
Check:
1400 + 210 = 1610
1.15 x 1400 = 1610 yay!