I'm thinking 1.2, increment 2 unless user does a long press on the "next" button (obscure UX, I know)
Long press opens modal, allowing to enter completely new name or buttons with part of the problem to increment. Ex: long press "next" on problem titled 1.2a will have an input box and 3 buttons, 1, 2, & a. Pressing 2 will remove a and incr 2
1.2, increment2unless user does a long press on the "next" button (obscure UX, I know)1,2, &a. Pressing2will removeaand incr2