Answer:
m∠B = 90°
Step-by-step explanation:
Note that the figure given to you is a triangle, which has 3 angles, and the total measurement of 3 angles is = 180°.
Let m∠B = x
m∠A = 60°
m∠C = 30°
Set the equation:
m∠A + m∠B + m∠C = 180°
Plug in the corresponding numbers to the corresponding variables:
60 + x + 30 = 180
Isolate the variable, x. Combine like terms:
x + (60 + 30) = 180
x + (90) = 180
Isolate the variable, x. Subtract 90 from both sides:
x + 90 (-90) = 180 (-90)
x = 180 - 90
x = 90
m∠B = 90°
