Select from the drop-down menus to correctly complete the statements. By the triangle sum property, m∠2+m∠3+m∠4=180∘ . The sum of the measures of angles Choose... is 180° because they Choose. Using the substitution property, m∠2+m∠3+m∠4=m∠1+m∠3. Then, by the subtraction property of equality, m∠2+m∠4=m∠Choose.