3. The y-intercept is the point on the graph where x = 0. Every time x increases by 1, y increases by 3. Let's take the ordered pair (2, 4). If we subtract 2 from x to make it 0, we subtract 6 from y, making the answer -2.
4. Two sets of ordered pairs cannot have the same x value in order to represent a function. So, the answer here would be C.