Is my answer right, if not what is the correct answer

What number must you add to complete the square x^2+12x=16

1234567891011 match the reasons with the statements in the proof. given: j | | k m 1 = m 3 prove: l | | m 1. j||k, m∠3 = m∠1 if lines are ||, then corresponding angles are =. 2. m∠1 = m∠2 if alternate interior angles are =, then lines are ||. 3. m∠2 = m∠3 substitution 4. l||m given

Factor the expression using the gcf. the expression 21m−49n factored using the gcf