The coordinates of trapezoid abcd are a(−4, 3), b(2, 3), c(4, −1) and d(−4, −1). a line segment runs through the trapezoid with endpoints y(−4, 1) and z(3, 1). if trapezoid abcd is dilated by a scale factor of 3 creating the new trapezoid of a′b′c′d′, what can you say about the length of line segment y′z′?

The distance from point Y to the y-axis is 4 units and the distance from point Z to the y-axis is 3 units, then the lelgth of the segment YZ is 4+3=7 units.
If a scale factor is 3, then the length of Y'Z' will be 7·3=21 units.

P.S. In the added picture you can see trapezoid ABCD that was dilated by a scale factor 3 about the origin. This may help to understand that all linear values after dilation become multiplied by scale factor.

You would plot 83 on the 83 line and you would plot -113 on the -113 line.