The formula to calculate the area of a circle is π*r^2, where r is the radius and pi is 3.14159265358979......

With that said, we could calculate the area of the outer red ring, but we just know the diameter. Since the radius is half the length of the diameter, the area of the ring will be 25π - (8/2)^2π , since the red ring is the different of the two circles.

Using the same logic, the red ring smaller than that is 5π, and the red circle in the middle is 1π. Adding those numbers together, we will get

9π + 5π + π

The answer to this problem is 15π.

I hope this helped,

Supermanaccz