Idon't know where to start on this problem.

It'd be helpful to you and possible helpers if you'd please include the instructions for the problems you post.  In this case you are asked to combine (add) two terms with the same denominator:  5.

Thus, the given expression becomes  (2sqrt[6] + sqrt[6]) / 5.
Combine 2sqrt[6] and sqrt[6] to obtain 3sqrt[6].  Divide this result by 5.

Correct                    3 sqrt(60
                                           
                                                    5

.7431448255...

i entered sin(48) into my calculator and got the answer above