Answer
It is the graph of y = 3x translated 6 units upward.
Explanation
The general equation for a straight line is y = mx + c where m and c are gradient and y-intercept respectively.
The graph of y = 3x is a straight line with a positive gradient of 3. It passes the origin.
The graph y = 3x + 6 is a straight line with the same gradient of positive 3. But this graph passes through the point (0,6). That is it cats the y-axis at 6.
So, the graph of y = 3x translated 6 units upward.