Answer: Choice B
They traveled 250 miles in 4 hours. Their speed was 62.5 mph.
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Step-by-step explanation:
Start at point X. Draw a horizontal line straight across until you reach the y axis. You should arrive at y = 250. This tells us that they traveled 250 miles.
Go back to point X. Draw a vertical line until you reach the x axis. You should reach x = 4. This indicates 4 hours.
Pairing up the two values together means they traveled 250 miles in 4 hours. Divide the distance over time to get the speed
speed = distance/time = 250/4 = 62.5 miles per hour
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Side note: unfortunately your teacher chose the label uppercase X for the point, which may be a bit confusing since it could clash with the lowercase x along the horizontal axis.
Another note: the speed represents the slope of the line