Let the initial quantity of grains be $x$. The first customer buys half of $x$ plus 3 kg, leaving $\frac{x}{2} - 3$ kg. The second customer then buys half of the remaining grains plus 3 kg, leaving $\frac{x}{4} - 3$ kg. The third customer buys half of what is left plus 3 kg, leaving 0 grains. Thus, we have the equation:
$\frac{x}{8} - 3 = 0 \implies x = 42$
\(\text{The number of solutions of the equation}\)\(\left(\frac{9}{x}-\frac{9}{\sqrt{x}}+2\right)\left(\frac{2}{x}-\frac{7}{\sqrt{x}}+3\right)=0\mathrm \; {is:}\)
If the set of all values of \( a \), for which the equation \( 5x^3 - 15x - a = 0 \) has three distinct real roots, is the interval \( (\alpha, \beta) \), then \( \beta - 2\alpha \) is equal to