Given that .

Since the bases of are congruent so .

Let .

    (Angle sum theory)

                                     (Substitute values)

                                         (Add: )

                                                 (Subtract 72 from each side)

                                                      (Divide each side by 2)

So,

Since forms a linear pair.Solve for .

                       (Linear pairs are supplementary)

                                 (Substitute )

                                         (Subtract 54 from each side)

Since the bases of are congruent so .

Let .

         (Angle sum theory)

                                    (Substitute values)

                                        (Add )

                                                     (Subtract 126 from each side)

                                                      (Divide each side by 2)

.

The measure of is 27, the right choice is A.