don't know how to do it

Hello Ziv, we have a couple of things here that we need to know before gettin around how the code works.

First, you have a variable called name that stores the name "Ziv" which is a string value(always keep track of how your variables work and what they have, in this case is a simple scalar value such as a string)

You then introduce another variable subject that stores the result of a format expression by creating a string that parses in information via the format built in function. Notice in your code that you pass a non existent variable called ziv. This is not what you want, you want to use the information STORED inside of your variable name which is ziv, so we could very well do this in this way:

name  = "Ziv"
subject = "Treehouse loves {0}".format(name)

# Another way of doing it albeit the first option is better

subject = "Treehouse loves {0}".format("Ziv")

Why do we pass the 0 into the {}? well it is quite simple, arguments passed to the format function have a numerical order, and in almost all computer programming languages we start counting at 0, the next would be 1 and so on.

If you wanted to pass more arguments you could do this:

original_poster = "Ziv"
this_commentor = "Alex"

subject = "Treehouse loves {0}! but they also love {1}!!".format(original_poster, this_commentor)

and that is basically it! Do not forget that you can type help(<function name>) in the interactive shell to get more information or look into the comprehensive python documentation!

# inside the python shell

help("".format)

The result is an explanation in which you can find some info regarding the function, notice that in order to get the information I had to give the help() function an example of the function that I am looking into!

hope that helps!