A full bathtub will empty at an average rate of 10 minutes. It will fill up to full at an average rate of 8 minutes if the plug is in. How long will it take to fill up to full if the plug is removed and the tap is turned...
8. A man walks for x hours at a speed of (x+1) km/h and cycles for (x - 1) hours at a speed of (2x + 5) km/h. If the total distance travelled is 90 km, find x.