Answer :
Use the equation: 3.142r+2r= 25.71
Combine like terms for: 5.142r = 25.71
You will find that the radius is 5. The diameter is 10.
If you are using 3.142 to represent pi, you can check using the formula for perimeter of pi times diameter/2 for a semi circle. Don't forget to add the line segment for the rest of perimeter.
It would look like this: SemiCircle: 3.142(10)/2 = 15.71(distance around semi circle) + 10 (the line segment) = 25.71
