Pre algebra assignment 5, algebra homework help

1)Martha can rake the leaves in her yard in 2 hours. Her younger brother can do the job in 6 hours. How long will it take them to do the job if they work together? show work

2)On a map, the length of a nature-center trail is 10.5 cm. If the scale is 1 cm to 21 km, what is the actual length of the trail? Round your answer to the nearest tenth, if necessary. show work

3)A boat goes 150 miles downstream in the same time it can go 120 miles upstream. The speed of the current is 77 miles per hour. Find the speed of the boat in still water. show work

There is 7 more questions which are attached below ( in this category if its multiple choice just pick an answer but if its not multiple choice then show me work)

total = 10 questions