To find \( x \), we start by noting that angles \( EAF \) and \( FAB \) are adjacent angles that share the line EB. Therefore, we can set up the equation:
\[ \text{measure of } \angle EAF + \text{measure of } \angle FAB = 180^\circ \]
Given:
- \( \text{measure of } \angle EAF = 4x \)
- \( \text{measure of } \angle FAB = 2x \)
Substituting these values into the equation gives us:
\[ 4x + 2x = 180^\circ \]
Combining like terms:
\[ 6x = 180^\circ \]
Now, divide both sides by 6:
\[ x = \frac{180^\circ}{6} = 30^\circ \]
Thus, the solution is:
\[ x = 30^\circ \]
So, the correct answer is 30°.