10.5 is 30% of what number?            (Write the question)

                                                        (Write percent equation)

                                        (Substitute 10.5 for a and 30 for p)

                                          (Write percent as decimal)

                                     (Divide each side by 0.3)

                                                       (Cancel common terms) 

                                                     (Divide: )

is the solution.