9514 1404 393
Answer:
z = 20
m∠A = 70°
Step-by-step explanation:
Step 0: read and understand the question. Identify the given information and the information requested.
Step 1: consult your knowledge of inscribed quadrilaterals to determine that opposite angles are supplementary.
Step 2: identify angles A and C as being marked with expressions in z.
Step 3: use those expressions and the relation in Step 1 to write an equation.
A + C = 180°
(4z -10)° +(10 +5z)°= 180°
Step 4: solve for z.
9z = 180 . . . . simplify, divide by °
z = 20 . . . . . . divide by 9
Step 5: use the relation between z and the measure of angle A to answer the question.
m∠A = (4z -10)° = (4·20 -10)°
m∠A = 70°
Step 6: check your answer. This can be done by making sure that angle C is supplementary to angle A.
C = (10 +5z)° = (10 +5·10)° = 110° = 180° -70° ∴ answer checks OK
