What percent of 70 is ?        (Write the question)

                                                        (Write percent equation)

                                     (Substitute for p and 90 for b)

                                   (Substitute for k)

                                           (Add: )

                                      (Divide each side by 70)

                                                       (Cancel common terms) 

                                                (Divide: )

                                              (Write decimal as percent)

is the solution.