Emily is three years older than twice her sister mary’s age. the sum of their ages is less than 30.

let x represent mary's age.

which inequality represents mary’s possible age?

a. 0 < x < / = 9
b. 0 < x < / = 18
c. 0 < x < 18
d. 0 < x < 9

If m∠abc = 70°, what is m∠abd? justify your reasoning.  using the addition property of equality, 40 + 70 = 110, so m∠abd = 110°.  using the subtraction property of equality, 70 − 30 = 40, so m∠abd = 30°.  using the angle addition postulate, 40 + m∠abd = 70. so, m∠abd = 30° using the subtraction property of equality.  using the angle addition postulate, 40 + 70 = m∠abd. so, m∠abd = 110° using the addition property of equality.