Data Sufficiency

In the xy-plane, points A, B and C are not on the same line. Is the slope of line BC negative?

1. The slope of line AB is -1.
2. The measure of angle ABC is 37 degrees.

Target question: Is the slope of line BC negative?


We can quickly see that statements 1 and 2 (alone) are NOT SUFFICIENT.

This brings us to...
Statements 1 and 2 combined
If we draw the line segment AB with slope -1, then we get something like this:


If we add some lines parallel to the x- and y-axes, we need to recognize that we get 45-degree angles at point B


So, if we add a 37-degree angle at point B, we get two possible scenarios:
Scenario #1

or
Scenario #2


In BOTH possible scenarios, the slope of line BC is definitely negative.
Since we can answer the target question with certainty, the combined statements are SUFFICIENT

Answer = C

Cheers,
Brent