Answer:
7 and 13
You can set up a simple equation to solve this: x + (2x-1) = 20
The x stands for the second, smaller number because the larger number is one less than twice it. When added together, they equal 20.
Now, you just solve for x. It goes as follows:
x + 2x - 1 = 20
3x - 1 = 20
3x = 21
x = 7
Since one number is 7, the other number has to be 13 to add up to 20.
Hope this helps!!! :)