Answer:
See picture below
Step-by-step explanation:
In order to do this, we need to understand what is happening here. As the final product is an alkene and triphenylphosphine oxide, means that the starting reaction was held using methyl-triphenylphosphine. In other words, a wittig reaction which is commonly used to convert ketones or even aldehydes into alkenes.
The first step involves, a nucleophilic attack from the triphenylphosphine to the carbonyl of the ketone.
The second step, the lone pair of the oxygen will go to the atom of phosphorus in the triphenyl to form a complex there.
Following this step into the 3rd step and final step we have a breaking of the bond C - P, and then, the oxygen along with the triphenylphosphine will leave the molecule as leaving group to form the final product.
See the picture below for mechanism and a better understanding
Hope this helps