Janie was given (-2, 3) as the endpoint of a line segment and (0,1) as its midpoint, which ordered pair should janie choose as he other endpoint?

When given two end points of a segment say for example (X1,Y1) and (X2,Y2) to get the midpoint of the line or the segment we use the formula,
 midpoint =( (X1+X2)/2 , (Y1+Y2)/2 )
therefore in our case the midpoint is (0,1)
hence, (-2 + X2)/ 2 = 0, thus X2 = 2
        and (3 + Y2)/ 2= 1 , thus Y2 = -1
Therefore the other end point will be (2,-1). Thus none of the above paper can be used as the other end point.

Density= Mass divided by Volume, but you're trying to find Volume so you apply Algebra and get Volume= Mass divided by Volume.

Volume= 0.5592841163 [kg/m (power to the 3)]

You should round it up