Levi watched as Hanji ran around her lab making a mess doing "experiments". She haven't paid attention to him once in the past three hours he had been waiting for her.
"Hanji." He said, and getting no reply he said it louder. After doing this for five minutes he just left a piece of paper on her desk and went to go tell Eren to clean.
Hanji saw him walk out. She meant to say hi but she just got a idea so she did that first, she didn't know it was going to take so long. Hanji went to go get a paper for the research when she saw it.
"Oh a math problem? 128 square root of e980," she looked at it, "what the fuck?"
It spread around the headquarters that Hanji had been working on a single math problem for the past three days with no sleep or food. Every time Moblit would go down there to try to force her to eat she would be staring at the problem. Moblit worried so much to the point where Levi went down to try to get her to eat, it was him after all who gave her the problem.
"Yo shitty glasses." Levi said when he went down with some bread.
"Hey there shortie" Hanji said smiling.
"What are you smiling at?" Levi asked, "and what about that problem?"
"Oh I gave up a while ago." She said her smile getting bigger. Levi looked at her and wanted to smile too.
"Good. Here some bread that assistant of yours was worried." With that Levi set down the tray and shut the door on the way out. Once it was shut though he leaned against it wondering what made him think it was a good idea to give her that.
"Hey Levi?" Hanji called out, "I love you too."
So she had solved it.