Can someone give me the answer :( and then explain how to get the answer..

x=months

so erica: 200+75x

darrell: 350+50x

make them equal:

200+75x=350+50x

get x on one side.

125x=550

500/125=x

x=4.4

for finding the midpoint of any given 2 pair of points simply add the respective x coordinates with other x coordinate and the y coordinate with other y coordinate and divide them by 2

in your question it will be :

(3+1)/2 for the x coordinate of mid point i.e 2

[8+(-4)]/2 for the y coordinate of midpoint i.e 2

so coordinates of mid point of points (3,8) and (1,-4) will be (2,2)

noncoplanar points are points that do not lie on the same line.