Let us have a denote the measure of the missing arc length. Since all circles measures 360°, it is then understood that all circles have an angle of 2π .
substitute values: <u> a </u> = <span><u> 120° </u> </span> 2π 360° multiply them by 2π and cancel out 2π so you will have a = <u> 24 </u> π<u> </u> 36 Simplify 24/36 π--2/3π. Thus, the answer to this item is the third option.
(See attached file for clearer work) <span><u /> <u /></span>