Geometry

Question Analysis:
This problem gives algebraic expressions for two opposite sides, and states they are parallel.
The main focus is applying the rule: one pair of opposite sides parallel and congruent ⇒ parallelogram.

Key Concept Explanation:
EF // GH, so we ensure EF = GH to form a parallelogram.

Step-by-Step Solution:
5x − 1 = 2x + 8
Subtract 2x: 3x − 1 = 8
Add 1: 3x = 9
Divide: x = 3

Common Mistakes:
Plugging in values without...