From the statement of the problem, we know that the perimeter of the hexagon in the figure is:
![P_{\text{hexagon}}=30.](https://img.qammunity.org/2023/formulas/mathematics/college/kfxphpobgdxwjeqwkirngqx48fzkb5h4vo.png)
The perimeter is equal to the sum of the lengths of the sides. So each side of the hexagon has a length:
![L_{\text{hexagon}}=(30)/(6)=5.](https://img.qammunity.org/2023/formulas/mathematics/college/rcf31wcw7t52waad68j8jr59fd1nbm4763.png)
The triangle inscribed in the hexagon is equilateral, so its three sides are equal. We see that the side AB of the triangle is also a side of the hexagon, so we have:
![L_{\text{triangle}}=L_{\text{hexagon}}=5.](https://img.qammunity.org/2023/formulas/mathematics/college/g3eyptbbe5fwlf9wzdwrlfcvophf2fcyta.png)
The perimeter of the triangle is equal to the sum of the lengths of its sides, so:
![P_{\text{triangle}}=3\cdot L_{\text{triangle}}=3\cdot5=15.](https://img.qammunity.org/2023/formulas/mathematics/college/yjkmwez9c3443h8oam60pduhu4m0pumkk8.png)
Answer
The perimeter of △ABC is 15.