Answer: Quadrant III
Explanation:
Let's pick example values for m and b
I'll go for m = -2 and b = 5. Anything works as long as m is negative and b is positive.
We go from y = mx+b to y = -2x+5
Plot this graph as shown below. The line passes through quadrants I, II, and IV. Only quadrant III is not touched at all.
