Story of Colors (Part 5)

Teacher: "JUNICHI!!"
Junichi: "*zzz...*"
Teacher: "Junichi Matsui!"
Junichi: "o..." (wakes up from his slumber)
Teacher: "You're sleeping again, you'd better concentrate, go wash your face"

***Junichi walks out***

Name: Junichi Matsui (松井 准一)
Gender: Male
Age: 17
Character attributes: Smart but very lazy

Eri: "I wonder what could his previous semester grade be"
Lyra: "Very poor perhaps"

The class continues when Junichi came back.

The teacher then starts teaching Mathematics. Everyone in class listens attentively until things get boring. Junichi starts to fiddle around with his pencil case, taking out pencils, pens and starts drawing on his notebook.

***Draw draw draw, sketch sketch sketch***

Suddenly!

Teacher: "Junichi! What are you doing! How dare you draw on your notebook!"
Junichi: "he... he..."

The teacher walks over and takes his notebook, inside were full of drawings and sketches; [beautiful, I would say]. Angrily, the teacher calls him out.

Teacher: "Now! solve this problem, or else detention for you today!"

Junichi winks at the teacher, then picks up the chalk and starts scribbling the solution on the blackboard.
A while later, the teacher checks his answer. What a shock she had! In fact, what a shock the entire class had.
Junichi then turns and walks gleefully back to his seat.
On the other end of the class, Eri and Lyra stares at the blackboard and with awe at Junichi.

PART 5 END

What exactly was with Junichi's answer? Was it a brilliant solution? Find out in Part 6. Bye!