Final answer:
In the poem 'Speaking with Hands', the mother starts an argument with the cash register out of frustration with their financial situation.
Step-by-step explanation:
In the poem 'Speaking with Hands', the mother starts an argument with the cash register because she is frustrated with their financial situation. The mother's argument with the cash register symbolizes her larger frustrations and feelings of powerlessness in life. She sees the cash register as a representation of their limited resources and the struggle to make ends meet. The poem explores themes of poverty and the impact it has on individuals and families.