Need help 1-4 , thanks!!

What is the missing reason in step 5? linear pair postulategivendefinition of complementary anglescongruent complements theorem

The ratio of the measures of the three angles in a triangle is 2: 9: 4. find the measures of the angels

William invested $5000 in an account that earns 3.8% interest, compounded annually. the formula for compound interest is a(t) = p(1 + i)t. how much did william have in the account after 6 years? (apex)