An air traffic controller spots two planes at the same altitude converging on a point as they fly at right angles to each other. One plane is 150 miles from the point moving at 450mph. The other plane is 200 miles from the point moving at 600mph. a) At what rate is the distance of the planes decreasing?
b) How much time does the air traffic controller have to get one of the planes on a different flight path?

Can someone explain the elimination method to me for this problem?

Dropping less than two inches per mile after emerging from the mountains, a river drains into the ocean. one day's discharge at its mouth, 5.6 trillion gallons, could supply all of country a's households for seven months. based on this statement, determine how much water an average household uses each month. assume that there are 100 million households in country a. country a uses approximately nothing gallons per household per month.

Solve this system of equations. 12x − 18y = 27 4x − 6y = 10