Explain why all of the graphs in this lesson show the first quadrant but omit the other three quadrants

Which best describes the strength of the correlation, and what is true about the causation between the variables? it is a weak negative correlation, and it is not likely causal. it is a weak negative correlation, and it is likely causal. it is a strong negative correlation, and it is not likely causal. it is a strong negative correlation, and it is likely causal.

How many $20 bills do you need to have to make $280

Which equation results from adding the equations in this system? x+6y=9 and -x+2y=-15