If a+b=2c, find $${a\over a-c}+{c\over b-c}?$$

$${3x+4y-2z+9=17},{7x+2y+11z+8=23}$$ and $$ {5x+9y+6z-4=18}$$ then what is  the value of $$ {x+y+z-34}$$?

(x+2y) (x² + 4y² – 2xy) equal to- 

If $$ {x+{1\over x}}=3$$ then find the value of $$ {x^2}-{1\over {x^2}}$$:

If then the value of

If a+b=17,and a – b =9, then the value of $$ {(4a^2+4b^2)}$$ is:

If a+b = 1 and a³+b³+3ab=k, then the value of k is : 

If average of two x and $$1\over x$$ (where x ≠ 0) is A, what will be the average of x³ and $$1\over {x^3}$$?