This is geometry Given: Triangle ABC

Prove: m∠A=60°

Triangle A B C with angle B being the right angle. Angle A measures open parenthesis 3 x close parenthesis degreed. Angle B measures open parenthesis x plus 10 close parenthesis degrees.

By the triangle sum theorem, the sum of the angles in a triangle is equal to 180°. Therefore, {Response area. }Using the (Response area,) (3x)°+90°+(x+10)°=180°. To solve for x, first combine like terms to get 4x + 100 = 180. Using the subtraction property of equality, 4x = 80. Then, (using the Response area), x = 20. To find the measure of angle A, use the substitution property to get m∠A=3(20)°. Finally, simplifying the expression gets m∠A=60°.

answer choices:
addition property of equality
substitution property
divison property of equality
distributibe property
m m