The problem in the image shows a triangle with three angle expressions involving $z$ and $c$. The interior angles of any triangle sum to 180°. Let's analyze the angles provided in the image.

The angles are:

1. $2z$ (bottom left angle)
2. $8z - 31^\circ$ (top angle)
3. $25c - 26^\circ$ and $11z - 47^\circ$ (bottom right angle, exterior)

For the internal angles of a triangle:

• The sum of the internal angles should equal 180°.
• Using this, we can solve for $z$, since there are two expressions involving $z$, but one exterior angle, which also uses $z$.

I will now calculate $z$, assuming we focus on expressions directly related to $z$ and the interior angles. Please confirm if the variable $c$ is needed for calculation or if it's meant to focus just on $z$.