We are given a diagram where $PQ$ is a straight line. We have angles $x$, $y$, $z$ and $m$ such that $m = \frac{1}{2}(x + y + z)$. We need to find the value of $m$.

1. Problem Description

We are given a diagram where $PQ$ is a straight line. We have angles $x$, $y$, $z$ and $m$ such that $m = \frac{1}{2}(x + y + z)$. We need to find the value of $m$.

2. Solution Steps

Since $PQ$ is a straight line, the sum of angles $x$, $y$, $z$ and $m$ is equal to 180 degrees.

$x + y + z + m = 180$

We are given that $m = \frac{1}{2}(x + y + z)$.

Multiplying both sides by 2, we get $2m = x + y + z$.

Substituting $x + y + z = 2m$ into the equation $x + y + z + m = 180$, we get

$2m + m = 180$

$3m = 180$

$m = \frac{180}{3}$

$m = 60$

3. Final Answer

The value of $m$ is $60^\circ$.

Answer: B. 60°