Slope of any line is the angle by which any line is inclined to the x axis.Slope is the ratio of rise and run.
Slope =
.The vertical change between two points is called the rise, and the horizontal change is called the run.
In the given question Marty's has a slope
and Ethan has a slope
.
As the slope is positive the line will move up then right.Line with slope .Marty is haveing a greater slope than Ethan.
In second case Marty's slope is
and Ethan slope is

Here Marty will have a greater slope.