We are given the total earnings of the school, $2800.
The earnings of each grade level are as follows:
2nd grade = $200
5th grade = $200
kindergarten = 2 * $200 = $400
4th grade = 2 * $200 = $400
1st grade = 3rd grade = x
The amount which is left for us to determine is the earnings of the first and third grade. This can be determined by equating all earnings to the total school earnings and let 1st and 3rd grade be the variable x:
$2800 = $200 + $200 + $400 + $400 + x + x
$2800 = $1200 + 2x
$1600 = 2x
x = $800
Therefore, 1st grade and 3rd grade earned $800 each.
