For "downhill" lines, if the rise is positive, the run must be positive?

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.

Awater holding tank measures 105 m long, 50 m wide, and 8 m deep. traces of mercury have been found in the tank, with a concen- tration of 60 mg/l. what is the total mass of mercury in the tank? answer in units of kg.

Which line is parallel to the line that passes through the points (2, –5) and (–4, 1) a. y=-x+5 b. y=-2/3x+3 c. y=2/3x-2 d. y=x+5