Answer:
24
Step-by-step explanation:
A pair of angles of a straight line are two angles that are adjacent to each other and share a common vertex. The sum of the measures of a pair of angles of a straight line is always equal to 180°.
Using this, we have:
84° + (4x)° = 180°
Subtract 84° on both sides:
84° + (4x)° - 84°= 180° - 84°
(4x)° = 96°
Divide both sides by 4.

We get
x = 24°.
Therefore, the measure of x is 24.