Answer:
²¹/₂₉
Explanation:
The sine of an angle is defined by: the length of the side opposite the angle ÷ the length of the hypotenuse. (SOH CAH TOA)
The length of the side opposite ∠B is 21 units, and the length of the hypotenuse is 29 units.
So, the ratio will be ²¹/₂₉.