To find the slope you use the slope formula y2-y1 / x2-x1. So use two point on the line we will make ours (1,2) and (3,4). Substitute to make 4-2 / 3-1 = 1/1 so using the rise over run method. The line rises up one and runs by one. The slash mark means divide, it's easiest in a fraction.
Also if you come across the equation y=mx+b, m is the slope and b is the y-intercept, this is called slope intercept formula.
I'm pretty sure the answer is "A matrix separates rational and irrational numbers." (Note: I'm not that great with memorizing definitions, but I'm pretty sure.) Hope this helps :)
