In a geometric figure with two intersecting lines, vertical angles are equal. Since \( \angle 1 \) and \( \angle 3 \) are vertical angles, we know that:
\[ m\angle 1 = m\angle 3 \]
We are given that \( m\angle 1 = (4x + 26)^\circ \) and \( m\angle 3 = 98^\circ \). Setting those equal to each other gives us the equation:
\[ 4x + 26 = 98 \]
Now, let's solve for \( x \):
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Subtract 26 from both sides: \[ 4x = 98 - 26 \] \[ 4x = 72 \]
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Divide both sides by 4: \[ x = \frac{72}{4} \] \[ x = 18 \]
So, the value of \( x \) is 18.