Can you help me solve this inequality?

[Cubist]

Spoiler: For Eugenio, not for S.A.M

Ok, that´s the reason. But that's not incorrect math. It's a mistake. Thanks for pointing it.

You're welcome. Your method would have been excellent if the question was slightly different! I was just concerned that S.A.M would copy it and then just disappear from the forum. I certainly don't want to put you off helping. It can be very rewarding! You're right that it isn't good for people to become too frustrated with a problem, but I don't think that S.A.M has been working on this continuously for all this time (at least I very much hope not) It's good if we can guide people towards the solution, so that they can have that satisfying "ahhh" moment when they get the answer (mostly) themselves.

Some of the posts here aren't from students, like carpenters trying to build a particular shape, etc. It's OK to provide a more direct answer in that scenario.

It's interesting that for some reason your approach gets the correct final answer, I haven't worked out why yet!