x values are your input, y values are your output. with that in mind:
1. (6, 2) and (15, -4) are your points. with two points, you can calculate a slope:
m = (y2 - y1)/(x2 - x1)
m = (-4 - 2)/(15 - 6)
m = (-6)/(9)
m = -2/3
your slope is -2/3.
to get your y-intercept, you need to plug in one of your points into point-slope form:
y - y1 = m(x - x1)
y - 2 = (-2/3)(x - 6)
y - 2 = (-2/3)x + 4
y = (-2/3)x + 6
repeat the same process for number 2.
(3, -.2) and (.2, -1.88)
(-1.88 - - .2)/(.2 - 3)
-1.68/-2.8
m = 0.6
y + .2 = 0.6(x - 3)
y + .2 = 0.6x - 1.8
y = 0.6x - 2