Assume that lines which appear to be tangent are tangent.
Find the value of the?

Answer:
12
Step-by-step explanation:
Assume that lines which appear to be tangent are tangent.
Therefor this is a right triangle.
Use the pythagorean theorem
c^2 = a^2 + b^2
15^2 = ?^2 + 9^2
225 = ?^2 + 81
subtract 81 from both sides
144 = ?^2
Take the square root of both sides
12 = ?
9514 1404 393
Answer:
? = 12
Step-by-step explanation:
The tangent makes a right angle with the radius at the point of tangency. That means the Pythagorean theorem can be used to find the missing length.
?² +9² = 12²
?² = 225 -81 = 144
? = √144 = 12
The value of ? is 12.
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Additional comment
When you see a right triangle with the ratio of hypotenuse to leg of 15:9 = 5:3, you know immediately that it is a multiple of a 3:4:5 right triangle. Here, the scale factor is 3, so the missing side is 3×4 = 12.