Answer:
biologists have a 14ft john boat with trolling motor for sale or trade for hipnopotomus
X = small van capacity, y = larger van capacity
y = x + 6
2x + y = 57
now we sub in x + 6 for y
2x + x + 6 = 57
3x + 6 = 57
3x = 57 - 6
3x = 51
x = 51/3
x = 17
y = x + 6
y = 17 + 6
y = 23
small van (x) has 17 seats and large van (y) has 23 seats
0.999993283193413 is the answer. You may have to round.
Measure the distance between the two end points, and divide the result by 2. This distance from either end is the midpoint of that line. Alternatively, add the two x coordinates of the endpoints and divide by 2. Do the same for the y coordinates.