Since \( \angle MAT \) and \( \angle TAH \) are supplementary angles, their sum equals \( 180^\circ \). Therefore, we can write the equation:
\[ \angle MAT + \angle TAH = 180^\circ \]
Substituting the given expressions for the angles:
\[ (6x - 6) + (4x - 14) = 180 \]
Now, combine like terms:
\[ 6x - 6 + 4x - 14 = 180 \]
This simplifies to:
\[ 10x - 20 = 180 \]
Next, add \( 20 \) to both sides of the equation:
\[ 10x = 200 \]
Now, divide both sides by \( 10 \):
\[ x = 20 \]
Thus, the solution for \( x \) is:
\[ \boxed{20} \]