Would you give this to a girl/guy?

Just because 'i' is typically the letter reserved for imaginary numbers does not mean it can be the only letter which can represent an imaginary number. "i" is a letter of convention, not an absolute.

a, z, and any letter in between can represent any number, any concept. So u = i and that's not an issue because i < 3i which still accurately reflects the equation.

In electrical engineering, j is normally used for imaginary numbers since i is normally the current.

Like Fiel said, letters can represent anything, they are not fixed, it just depends on what you defined a priori

i could also be the unitary vector of the system (i,j,k) of coordinate vectors

I know this thread is a bit old but I have to point this out:

1.) If you switch the sides instead of the sign when you divide by -7, you end up with 3u>i
2.) The end result reads "I am worth a third of your worth"; not the right line
3.) i (imaginary numbers) can't even be compared in an inequality
being srs in funhaus