Sometimes it's hard. Never too hard. No, Rodney's never really met a problem that he can't figure out in the end. (Even if he's full of jitters from his sixteenth cup of coffee.) He will figure this out and internally shouting eureka.
John had kissed him. Right there in the lab. They'd been arguing. (When weren't they arguing?) Rodney had notes and schematics on everything. He knows about Ancient ships and is the foremost expert on wormhole theory, in the Pegasus Galaxy anyway. Now he has new information on John, an addition to soldier, leader, brave, cute, pilot, intelligent. He's appended with gay, or bisexual (there were a few ascended women).
There's only one factor Rodney can't put in. Maybe he doesn't believe it. (Just like he took apart his sister's love of Sleeping Beauty metaphor by metaphor when he was eight and she was six.) But he's a genius and a scientist; he'll compute, calculate, and make a graph.
Rodney does figure it out when John tells him to shut up and stop thinking, pushing Rodney against the wall and kissing him again. John's mouth is sure and strong. Rodney almost falls on his knees and groans. (Like the first time he read "A Primer on Wormholes: The Physics of Maintaining Point-to-Point Matter Transfer" by Samantha Carter.) Somewhere he's freaking out. It's brain's yelling that John really does like him, that John really wants him.
The last equation of the formula clicks into place, and Rodney's tongue runs along John's bottom lip.