Let x, and y be the two numbers the problem is asking for, then we can set the following system of equations:
Solving the second equation for x, we get:
Now, substituting x=2y in the first equation we get:
Solving for y we get:
Finally, we substitute y=10 in the first equation on the board and get:
Solving for x we get:
Answer: the numbers we are looking for are 20 and 10.