Can someone explain to me how you would solve an equation like this, please? explain 5 or 6. you choose. (in the link below)

Sherrie is baking a pie for her family. she leaves the room and comes back to 35% of the pie having been eaten before she can put the topping on. how much 1 square inch strips of dough will she need for the top, now that a portion is missing? round your answer to the nearest while nimber.