Circle a has a radius of 3 and circle b has a radius of 11. if the idstance between the center of the circles in 17, find the length of the common external tangent

Use Pythagorean Theorem:
a² + b² = c²
"a" is one side of the right triangle.
Its length is: radius of larger circle minus radius of smaller circle: (11 - 3 = 8)
The distance between the center of the circles creates the hypotenuse (17)
8² + b² = 17²
       b² = 225
       b = 15

the length of the common external tangent is 15.