Okay. So, we're looking for the percentage of Celina's running speed as her walking speed. Her running sped is 8 mph and her walking speed is 4mph. All we have to do is 4/8 = x/100. You put change/original and x/100, because we're looking for the percent of change from running speed to walking speed. Cross multiply the values to get 400 = 8x. Divide each side by 8 to isolate the "x". 400/8 is 50. x = 50. Celina's walking speed is 50% of her running speed. The answer is B: 50%.
