A television poll of 151 persons found that 68 watched Law and Disorder; 61 watched Twenty-five; 52 watched The Tenors; 16 watch
ed both Law and Disorder and Twenty-five; 25 watched both Law and Disorder and The Tenors; 19 watched both Twenty-five and The Tenors; and 26 watched none of these shows. How many persons watched all three shows?
