If m∠A = m∠B and m∠A + m∠C = m∠D, then
m∠B + m∠C = m∠D.

True. The statement is also equivalent to: If m<B + m<C does not equal m<D, then m<A does not equal m<B and m<A + m<C is not equal to m<D.

The 90% confidence interval for the mean is (170.87 , 189.13)

Step-by-step explanation:

Using the calculator we can easily calculate   the 90% confidence interval for the mean, the given values are:

mean=180

sx : 38.5

n : 50

c - Level : 0.90

Then the output will be [170.87 , 189.13]