Answer:
<h2>
a ∈ (-∞, -3></h2>
Step-by-step explanation:
<h3>-
21 ≥ 3(a - 7) + 9</h3><h3>
- 21 ≥ 3a - 21 + 9</h3>
+21 +21
<h3>
0 ≥ 3a + 9 </h3><h3>
3a + 9 ≤ 0</h3>
-9 -9
<h3>
3a ≤ - 9</h3>
÷3 ÷3
<h3>
a ≤ -3 </h3><h3>
a ∈ (-∞, -3></h3>
Quadrilateral that is a parallelogram
This one is super difficult, I see your struggle but the answer is A.
