Let us start with the plane flying east at a slower speed. Let us assume that its speed is x kilometers per hour. After 4 hours, it will have traveled 4*x = 4x kilometers.
Now let us calculate the speed of the plane flying west. It is faster by 75 kilometers per hour than the other plane. So its speed per hour is x+75 kilometers per hour. After 4 hours, it will have traveled 4( x+75) = 4x+300 kilometers. The total distance traveled by both the planes is 5460 kilometers. In other words, 4x+4x+300 =5460 kilometers.
Now simplify the equation:
8x + 300 = 5460
8x = 5460 - 300
8x = 5160
x = 5160/8 645.
x is the speed of the plane flying east. It is 645 kilometers.
x + 75 is the speed of the plane flying west. It is 645 + 75 =
720 kilometers.
