Identical width of columns

Problem

There are two columns with different width. I need them to be identically wide.

Solution

I´ll select columns by clicking on their headings, which means on letters A, B, C...

If they are side-by-side (for example A and B or B and C), it´s easy. If not, I´ll click on the first one, then push Ctrl and click on the second one (and third one and so on...)

Then I´ll modify the widht of one of them - it does not matter which one - by dragging its right border in heading (between letters).

And, since I selected more of them, ALL columns will modify its width to the same size.
The same with rows...