-1 OR 3*2>999 --

It looks like a boolean expression with a trailing comment marker (--). Ignoring the comment, evaluate:

• 3*2 = 6
• 6 > 999 is false
• -1 is typically treated as truthy (nonzero)

So: truthy OR false = truthy.

What you get exactly depends on the language:

• Python: -1 or (6 > 999) evaluates to -1 (but bool(-1 or False) is True)
• JavaScript: -1 || (6 > 999) evaluates to -1 (truthy)
• C/C++: (-1 != 0) || (6 > 999) evaluates to 1 (true)
• SQL: this exact form is not valid SQL; booleans are expressed differently

If you tell me the language you’re studying, I’ll give a precise one-line result for that language.