The Secret Life of the American Teenager 5×19 “Interference” guest starring Danica McKellar – Ethan’s mission to put an end to algebra leads him to actress and mathematician Danica McKellar on an all-new episode of The Secret Life of the American Teenager, airing Monday, April 29th on ABC Family. Ethan is convinced no adult actually uses algebra, but a chance meeting with Danica McKellar helps him look at math in a different light. Amy’s frantic search for her missing wedding bands leads her to Ben, who advises her to break-up with Ricky before it’s too late. George and Kathleen’s romantic dinner is interrupted by an uninvited guest. Meanwhile, Mrs. Stone confronts Grace about her relationship with Jack.