4.(08.05) A student is trying to solve the system of two equations given below:
Equation P: a + b = 6
Equation Q: 4a + 2b = 19
Which of the following steps can be used to eliminate the a term? (4 points)
4(a + b = 6)
0 -1(4a + 2b = 19)
-4(a + b = 6)
0 -4(4a + 2b = 19)

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.