1. **State the problem:** We need to find the cost of 3 boxed lunches based on the given graph. 2. **Identify the relationship:** The graph shows a linear relationship between the number of boxed lunches ordered ($x$) and the total cost ($y$). 3. **Use the formula for a line:** The cost can be expressed as $$y = mx + b$$ where $m$ is the slope and $b$ is the y-intercept. 4. **Determine the slope and intercept:** The line passes through the origin $(0,0)$, so $b=0$. The slope $m$ is calculated by the change in cost over the change in number of lunches: $$m = \frac{30 - 0}{3 - 0} = 10$$ 5. **Write the equation:** $$y = 10x$$ 6. **Calculate the cost for 3 boxed lunches:** Substitute $x=3$: $$y = 10 \times 3 = 30$$ 7. **Conclusion:** The cost of 3 boxed lunches is $30$ dollars.