−1.23m=−0.492 A. m = 0.738 B. m = 0.60516 C. m = 0.4 D. I don't know.

ιт ωαѕ 5¢м вє¢αυѕє 1/4 σf 20 ιѕ 5

αи∂ 5*4=20

нσρє ι ¢συℓ∂ нєℓρ уσυ

arc length = radius * x ( in radians)

6 * pi = 18 * x

divide by 18 on each side

6 pi / 18 = x

pi/3 = x

the angle is pi / 3 radians

or   60 degrees

is there more info provided? there is not enough information given in the problem