The equation y=3x+4 can be compared to the stright line equation y=mx+c, where m is the slope and c is the y intercept.
Comparing the equations, the y intercept of the graph, c=4.
Also, the slope is m=3, which is a positive slope.
Only the first graph have a positive slope with the y intercept c equal to 4.
So, the first graph is represents
