Final answer:
The equation showing the proportional relationship between the distance Marco bikes (y) and the number of hours (x) is y = mx, where m is the constant speed at which he bikes.
Step-by-step explanation:
The student is asking for an equation that represents a proportional relationship between the distance Marco bikes, denoted as y, and the number of hours, denoted as x. Since the graph shows a straight line, we can use the equation y = mx + b, where m is the slope and b is the y-intercept. In this case, the y-intercept is zero because the graph starts at the origin, indicating that Marco hasn't traveled any distance at time zero. The slope of the graph, m, represents the rate at which Marco bikes, which is the constant speed. Therefore, the equation is y = mx, or if we want to use specific units, like in the equation y = (2.0 km/min) x, we would write it y = (2.0 km/min) × t where t represents time.