By the Response area, the sum of the angles in a triangle is equal to 180°. Therefore, m∠A+m∠B+m∠C=180°. Using the Response area, (6x)°+90°+(x+6)°=180°. To solve for x, first combine like terms to get 7x + 96 = 180. Using the Response area, 7x = 84. Then, using the division property of equality, x = 12. To find the measure of angle A, use the substitution property to get m∠A=6(12)°. Finally, simplifying the expression gets m∠A=72°.