If angle a is 60° and angle c is 30°what is the measurement of angle b ?

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°