## Elementary Algebra

Let t represent the time it takes the planes to be 1125 miles apart. The first plane travels at 350 miles per hour, for t hours, so the distance it flies is: 350 $\times$ t = 350t. The second plane travels at 400 miles per hour, for t hours, so the distance it flies is: 400 $\times$ t = 400t. The planes fly in opposite directions. To find the time it takes them to be 1125 miles apart, we set up the following equation: 350t + 400t = 1125. 750t = 1125 Divide both sides by 750: t = 1.5 It takes the planes 1.5 hours to be 1125 miles apart.