I don't know how to approach this question

Two cars are headed for the intersection of the two roads. ii CarA is travelling south at 41 km/h and car B is travelling east at 55 km/h, at what rate is the distance between the cars decreasing when car A is 9 km and car B is 8 km from the intersection? _ Note: Write only the numerical value of the rate. the units are already written. Write the exact answer not the decimal approximation (for example, write 1/2 but not 0.5). it the answer has a squre root then use the equation editor or use parentheses, tor example, for write (3)\"(1/2) do not write (3)\"{1/2) or (3)\"{1/2]. Answer: The distance between the cars is decreasing at a rate of ' a a kah