The graph of a line passes through the points (0,-2) and (6,0). what is the equation of the line?

Simple, using y1-y2 and x1-x2 method to find the slope,

take (0,-2) and (6,0)

and,

-2-0
over   (-2-0/0-6)
0-6

making it -2/-6=3

thus, your slope is 3.

but you're still not done, use slope and plug it into any of the points.

using (0,-2)

an equation in slope-intercept form is y=mx+b

thus,

-2=3(0)+b
-2=0+b
-2=b

thus, your equation is y=3x-2.