This is my first post so hello everyone!

I'm from china, my english isn't too good, please bare with me if you find my wording a bit wierd. I'll try my best to make myself comprehendable.

Here is the problem that gives me difficulty:

It takes Betty 2 hours longer to do a certain job than it takes Ada.They worked togeher for 3 hours then Ada left and Betty finished the job in 1 hour.How long would it take each of them to do the job alone?

I know I should let x hours be the time it takes for Ada to finish the job, then for Betty it shall be x+2 hours, however I can't figure out how to express Betty and Ada working on the same job for 3 hours in algebraic forumla, can anyone help me please?