Two linear equations problem.

I have two problems that I'm having a hard time solving.

Erin takes a total of 5 hours in her boat to travel a distance upriver and return downriver the same distance. If the time traveling upriver is twice the time traveling downriver, how many hours does each trip take?

I need to get 2 equations out of it and use the matrix to solve the problem...

The first equation I got from it is...

U + D = 5 and the second is 2U = D...?

The other problem I'm having trouble with is...

Monica lives 16 mi. from her job. One morning she decides to get some exercise by jogging part of the way and taking the bus the rest of the way. She estimates she can average 4 mi/h jogging and 20 mi/h on the bus. If she allows 1 hour to get to work, how many minutes should she jog and how many should she ride? Write one equation for time and one for distance.

I can't figure out the 2nd one at all. (Headbang)