1) Two planes are 1800 miles apart and are traveling toward each other. One plane is traveling twice as fast as the other plane. The planes will pass each other in 3 hours. Find the speed of each plane.
2) A jet plane flying with the wind flew 2100 miles in 4 hours. Against the wind, the plane could fly only 1760 miles in the same amount of time. Find the rate of the plane in calm air and the rate of the wind.
3) A merchant mixed 10 lbs of cinnamon tea with 5 lbs of spice tea. The 15 lb mixture cost $40. A second mixture included 12 lb of the cinnamon tea and 8 lb of the spice tea. The 20 lb mixture cost $54. Find the cost per pound of the cinnamon tea and of the spice tea.