The task is to generate the correct answer for a given math problem.

Problem: a man rows his boat 110 km downstream and 90 km upstream , taking 3 hours each time . find the speed of the stream ?
3.5

Problem: virginia , adrienne , and dennis have taught history for a combined total of 96 years . if virginia has taught for 9 more years than adrienne and for 12 fewer years than dennis , for how many years has dennis taught ?
4

Problem: 212 : 436 : : 560 : ?
784