Final answer:
An expression for the total amount spent on a shirt and jeans, with the shirt costing $20 and the jeans 'j' dollars, would be 20 + j.
Step-by-step explanation:
The student's question is about how to write an expression for the total amount spent on buying a shirt and jeans given the cost of the shirt is $20 and the cost of the jeans is represented by the variable 'j' dollars. The correct expression for the total amount spent would be 20 + j.
This represents the sum of the cost of the shirt ($20) and the variable cost of the jeans (j). This form of expression is commonly used in budget constraint equations, where we calculate the total spending based on the price and quantity of items purchased, given a person's budget.