$\"\"$

The measure of the median of a trapezoid is one-half the sum of the measures of the bases.

So, $\"\"$

$\"\"$ (Substitute $\"\"$ )

$\"\"$ (Combine like terms)

$\"\"$ (Distributive property)

$\"\"$ (Simplify)

$\"\"$ (Add 1 to each side)

$\"\"$ (Multiply 2 to each side)

$\"\"$ (Divide each side by 7) $\"\"$

The value of x is 4.