Low at my problem bending — Math Problem

Dickinson was not good at math. She blamed her fingers.

Low at my problem bending, ¹
Another problem comes－
Larger than mine－Serener－
Involving statelier sums.

I check my busy pencil, ⁵
My figures file away.
Wherefore, my baffled fingers
Thy perplexity?

(F.99/J.69)

[1] Low:: depressed. bend:: to yield, give way to; to prove pliant _{(OED 10)}. problem bending:: she was depressed by her surrendering to someone or something.
[2] Another problem:: a math test given by a teacher.
[3, 4] Serener, statelier:: a test quieter and statelier than her bending problem (a debate probably).
[4] sums:: arithmetic operations.
[5] pencil:: pencil, sums, problem, and figures are used to hint the answer.
[6] figures:: digits. file away:: to disarrange, tangle.
[7-8] Wherefore, fingers, perplexity:: she was perplexed by the math problem, and blamed her fingers.