simplify the following equation
$$ (1-{1\over3})(1-{1\over4})(1-{1\over5})......(1-{1\over n})$$

If , and y=2x, find x. 

The ratio of two unequal sides of a rectangle is 1 : 2. If its perimeter is 24 cm, then the length of diagonal in cm is:

If x – y + z = 15, xyz = -216 and xz – xy – yz = 18, then the value of

If 0.4 m + 0.8 n = 2.2 and 0.8 m + 0.4 n = 1.4, then the value of is equal to 

If then the value of will be

If then the value of is.

, then the value of is