How many postal codes begin with Y and end with digit 7?

The question you're asking is a bit complex because it depends on the country and its postal code system. However, I'll try to give a general answer.

In a hypothetical situation where a postal code system uses a single letter followed by a single digit (like 'Y7'), there would be only one postal code that starts with 'Y' and ends with '7'.

However, in many postal code systems, such as the Canadian one, the format is different. In Canada, the format is 'Letter, Number, Letter - Number, Letter, Number' (like 'Y1A 0B1'). In this case, the number of postal codes that start with 'Y' and end with '7' would be much larger.

To get an exact number, you would need to have access to a database of all the postal codes in the country you're interested in. Then, you could use a computer program to count how many of those postal codes start with 'Y' and end with '7'.

I hope this helps! If you have more specific information about the postal code system you're interested in, I might be able to give a more precise answer.