1. **State the problem:** We have a bar model representing the total price of a bowl of plain phở plus some extra ingredients. The bar is divided into 4 segments: one segment labeled $b$ (price of plain phở) and three segments each labeled $n$ (price of each extra ingredient). The total price represented by the entire bar is 13. 2. **Interpret the bar model:** The bar shows that the total price is the sum of the price of the plain bowl plus the price of 3 extra ingredients. 3. **Write the equation:** The total price is given by $$b + n + n + n = 13$$ 4. **Simplify the expression:** Since there are three $n$ terms, we can write $$b + 3n = 13$$ 5. **Complete the statement:** The price of a plain bowl plus the price of \textbf{3} extra ingredients equals \textbf{13}. This means the total cost of the plain bowl and the three extra ingredients together is 13.