Three positive numbers are in the ratio of 11 : 12 : 15. If the sum of the squares of those numbers is 1960, then the sum of the numbers is

If x+y=10 and xy=4, then what is the value of x⁴+y⁴=?

Simplification 

If x - y = 3, then what is the value of x³ - y³-9xy? 

If a-6b = 3 then the value of a³-216b³-54ab is : 

$$ {x+{1\over{x}}}$$, then the value of $$ {x^2}+{1\over{x^2}}$$ is

If $$ {(x+{1 \over{x}})^{2}}=3$$, the value of of $$  {x^{206}+x^{200}+x^{90}+x^{84}+x^{18}+x^{12}+x^{6}+1}$$