Answer:
? = 7.2
Explanation:
Remark
Is that a misshapen circle or is it an ellipse? I'm going to assume it is a circle, but if I am wrong, leave a comment. A tangent will meet a diameter's end at right angles which allows you to use the Pythagorean theorem.
Formula
a^2 + b^2 = c^2
Givens
c = 12
a = 9.6
b = ?
Solution
c^2 - a^2 = b^2
144 - 92.16 = b^2
b^2 = 51.84 Take the square root of both sides
sqrt(b^2) = sqrt(51.84)
b = 7.2