Two numbers x and y (x>y) such that their sum is equal to three times their difference. Then value of $$3xy\over 2(x^2-y^2$$ will be 

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

If , then the value of x

If a = 7, b = 5 and c = 3, then the value of is 

If then the value  of will be:

If  then find the value of

If then the value of will be

If then what is the value of (x+y-z)?