Here's the question you clicked on:
brwnchristo
what is the slope of y=5?
here's a hint: horizontal lines = 0 slope vertical lines = undefined slope so what do you think is y = 5? horizontal or vertical?
slope is rise/run rise is 0 and run is unknown therefore slope is 0
HOY - Horizontal, 0 slope, Y= a number! :) So in this case, slope would be zero. Also useful to know is VUX: Vertical, Undefined slope, and X = a number.
HOY and VUX are mnemonics, if you learn them, it will make your life a lot easier :D