Triggering an External Calculator with Calculation Annotation

Mechanism of Tool Invocation and Result Substitution

A user wants a language model to solve a word problem by showing its work and then providing a final answer. The model should format its calculations using ≪...≫ so an external tool can execute them accurately, and use #### to mark the final answer. Review the model's response below and identify the primary error in its formatting.

Problem: A farmer has 3 fields, and each field produces 150 bushels of corn. If the farmer sells 200 bushels, how many are left?

Model's Response: First, I need to find the total production. ≪There are 3 fields, so 3 * 150 = 450 bushels total≫. Then, the farmer sells 200 bushels. The remaining amount is ≪450 - 200≫. So the final answer is 250.

Applying Calculation Annotation Formatting

A developer is designing a system where a Large Language Model solves math word problems. The system must ensure arithmetic accuracy by offloading calculations to an external tool and must also present the final answer in a clearly identifiable way. Which of the following model outputs best applies a formatting strategy to achieve both of these goals?