Rationalize the denominator of the surd, giving your answer in the simplest form. Rationalize the denominator of the surd, giving your answer in the simplest form. $\frac {3}{\sqrt2+5} $ Please help me... It must be like this right? $\frac {3}{\sqrt2+5} * \frac{\sqrt2-5}{\sqrt2-5}$

Yes, you've got a great start. Now, simply multiply the numerators and the denominators,

$$\frac {3}{\sqrt2+5} * \frac{\sqrt2-5}{\sqrt2-5} = \dfrac{3(\sqrt 2 -5)}{(\sqrt 2 + 5)(\sqrt 2 - 5)}$$ - and in the denominator, use the fact that $$(a +b)(a-b) = a^2 - b^2$$