Does anyone know the answer?

Supplementary angles are two angles whose measures add up to 180° . The two angles of a linear pair , like ∠1 and ∠2 in the figure below, are always supplementary. But, two angles need not be adjacent to be supplementary. In the next figure, ∠3 and ∠4 are supplementary, because their measures add to 180° so

angle ∠ABC  90°  therefore subtract the 90 to 180 to get the final answer

180-90=90

Final Answer is ∠QRS 90

it is a. 4.2 because 7.6-3.4 gets the remaining length of 4.2. i might be wrong but i am pretty sure this is the answer.

if you are looking for the unit rate then the answer would be 9 because unit rate is distance divided by time.

step-by-step explanation: