1. The problem involves finding the angle $a$ at point $Q$ given some angles in the figure and using the variable $x$ at point $S$. 2. From the figure, angle at $P$ is given as 55°. 3. The triangle formed by points $P$, $Q$, and $S$ has angles $a$ at $Q$, 55° at $P$, and $x$ at $S$. 4. The sum of the interior angles in a triangle is always 180°, so we have the equation: $$a + 55 + x = 180$$ 5. Rearranging to find $a$, we get: $$a = 180 - 55 - x$$ $$a = 125 - x$$ 6. Without additional information about $x$, $a$ depends on $x$. 7. The problem states to use $x$ to find $a$, so this is the relationship: $$a = 125 - x$$