HI Agnes,

You have written the expression

\[\left( 1 + \sqrt{3}\right) \left( \frac13 + \sqrt{3}\right)\]

but I think what the expression should be is

\[\left( 1 + \sqrt{3}\right) \left( \frac{1}{3 + \sqrt{3}}\right)= \frac{1 + \sqrt{3}}{3 + \sqrt{3}}.\]

If I am correct then you need to "rationalize the denominator" by multiplying the numerator and denominator by

\[3 - \sqrt{3}.\]

I hope this helps,
Penny