To rationalize the denominator, you need to multiply numerator and denominator by the conjugate. The conjugate is the term in the denominator with the opposite sign. In other words, you will multiply top and bottom by sqrt(7) + 2
The numerator will be 5[sqrt(7) + 2].
The denominator will be 7 - 4 = 3. Why? We use the FOIL technique on the denominator, where FOIL = First, Outer, Inner, Last, referring to the terms of the binomial expression.
The final answer is 5[sqrt(7) + 2]/3
