Final answer:
To express the budget constraint for the selected projects, the inequality 900X₁ + 800X₂ + 700X₃ ≤ $2,000 is used, indicating the sum cost of projects chosen must not go over the $2,000 budget.
Step-by-step explanation:
To represent the constraint "Total cost of doing selected projects cannot be more than $2,000", we can use the prices of the projects and the variables X₁, X₂, and X₃ to stand for the quantity (or decision to undertake) of each project. The cost for undertaking project 1 is $900, project 2 is $800, and project 3 is $700, respectively. So, the constraint in terms of X₁, X₂, and X₃ would be:
900X₁ + 800X₂ + 700X₃ ≤ $2,000
This equation expresses that the total expenditure on the selected projects, which is the sum of the individual costs multiplied by the decision variables (i.e., the quantity of each project selected), cannot exceed the available budget of $2,000.