In a geometric diagram, ∠A and ∠B are complementary, and they form a straight line with ∠C . If m∠A=x° , m∠B=(2x)° , and m∠C=90° , what is the measure of ∠B ?(1 point)
180°
90°
30°
60°
Since ∠A and ∠B are complementary, their measures add up to 90°. We also know that ∠B has a measure of 2x°. So, we can set up the equation:
x + 2x = 90
Combining like terms gives:
3x = 90
Dividing both sides by 3 gives:
x = 30
Therefore, ∠B has a measure of 2x = 2(30) = 60°.
The measure of ∠B is 60°. Answer: \boxed{60°}.