I have a very basic question about how to express a certain range of rows
that I wish to delete in a macro. It's not tricky (I don't think), I just
haven't been able to find the right help file or webpage to explain the
phenomenon to me (I'm very new at this).

Basically I want to delete a number of rows based on a variable (integer).
If the variable is 1, for example, I want to delete rows 13-26. It is
possible for me to do this with the following line:

Worksheets("Math").Rows("13:26").Delete

The problem is, I can't figure out how I should do this when I want to bring
my variable into it. For example, I would love to be able to use:

Worksheets("Math").Rows(MyVariable * 13:MyVariable*13 + 13").Delete

But that's not the right syntax at all. Any suggestions?