I don't know and I don't care. At a glance I'd say 1, but like others said, it's intentionally ambiguous (which is the whole point of why you see these posted on Facebook and such) unless you rigorously apply some rule.
I'm a engineering professor and do simple arithmetic like this every day, but I haven't used a division symbol in 40 years and have no idea how to do one on the keyboard. The division symbol is shorthand for a fraction, it's a dot over another dot where the things before or after fill in the dots*.
Just use the fraction and use enough parentheses to make it clear if you're typing it in one line. Students still mess it up if I write it in one line even if I have the parentheses correct, so it's much better to use the equation editor and do it right.
*perhaps apocryphal, but it makes sense