Answer:
m∠A = 90°
Step-by-step explanation:
In isosceles triangle base angles are congruent. That means we can equate measurments of angle B and angle C and solve for x!
m∠B = m∠C
11x - 10 = 7x + 10
4x - 10 = 10
4x = 20
x = 5
Now let's insert x back in the expressions for angles.
m∠B = (11x − 10)° = (11(5) − 10)° = 45°
m∠C = (7x + 10)° = (7(5) + 10)° = 45°
Sum of all angles in the triangle is 180°. Let's make an equation.
m∠A + m∠B + m∠C = 180°
m∠A + 45°+ 45° = 180°
m∠A = 90°
