Beach Maths

In another life, I often used to talk to my students about a certain sort of maths being Beach Maths. What I meant at the time was a problem that required few words to pose and only pencil and paper to solve.
Obviously one of my pupils listened - a darling son had the misfortune to be a pupil as well as a dutiful son. One major advantage of this - besides the obvious plus for his mathematical education (or not) - is that on occasion he would call me "Sir" outside the classroom. The prospect of loss of street cred meant that he never called me "Dad" inside the classroom.
Either way he has recently taken to texting me a problem and the last one is here in the image. All you have to do is to add one straight line to make the sum correct.
For the purists it is not a well-posed problem as a line through the equal sign to make "not equals" clearly works. I was told in no uncertain terms that that was a rubbish suggestion.
The real solution works. I will leave you to spot it.