Answer: 11,682.4 miles
Step-by-step explanation:
We can think the planet as a circle:
if we have a circle of radius R, and an arc of A degrees in the circle, the lenght of the arc is:
L = (A/180°)*3.14*R
Here we know that:
L = 4076 miles
A = 20°
Then:
4076mi = (20/180)*3.14*R = 0.3489*R
R = 4076mi/0.3489 = 11,682.4 miles