SOLUTION
Given the question in the image, the following are the solution steps to answer the question.
STEP 1: State the appropriate side theorem that applies to the given question
Opposite sides of a parallelogram have equal lengths. This means that:
STEP 2: Write the measures of the two sides
STEP 3: Find the equation that applies
According to the statement in Step 1,
STEP 4: Solve for x
Hence, x = 9