Tell me the equation if the slope of a line is -1/2 and the y-intercept is 0

My math teacher told my class to "steal" a 6th grade fraction word problem from the internet, word problems? : -p requirements: only a 1 step word problem. needs to be complex.

Is the power produced directly proportional to the wind speed, give reasons for your answer?

If a and −a are numbers on the number line, which expression must give the distance between them? a) 0 b) a c) |2a| d) |a|