Find the number of all $2$-digit numbers divisible by $3$.

Find the values of $k$ such that the quadratic equation: $x^2-2kx+(7k-12)=0,$ has real and equal roots.

Find the value of $k$ such that the quadratic equation: $x(x-2k)+36=0,$ has real and equal roots.

Find the difference between the roots of the quadratic equation $3x^2-2\sqrt{6}x+2=0$.

Solve for $x$,

$\frac{2x-3}{x-1}-\frac{4(x-1)}{2x-3}=3; x\ne 1,\frac{3}{2}$