Problem Solving, need help forming the equation please

This is my first post so hello everyone! (Handshake)

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?