The problem asks us to find the size of angle $g$ in a pie chart. The pie chart is divided into three sections with angles $100^\circ$, $120^\circ$, and $g$.

1. Problem Description

The problem asks us to find the size of angle $g$ in a pie chart. The pie chart is divided into three sections with angles $100^\circ$, $120^\circ$, and $g$.

2. Solution Steps

The sum of the angles in a full circle is $360^\circ$. Therefore, the sum of the angles in the pie chart must be $360^\circ$.

We can write the equation:

$100^\circ + 120^\circ + g = 360^\circ$

Combine the known angles:

$220^\circ + g = 360^\circ$

Subtract $220^\circ$ from both sides of the equation to isolate $g$:

$g = 360^\circ - 220^\circ$

$g = 140^\circ$

3. Final Answer

The size of angle $g$ is $140^\circ$.