Write + or - in each \( \bigcirc \) to make each equation true. (a) \( \frac{13}{18} \bigcirc \frac{1}{9} \bigcirc \frac{1}{2} \bigcirc \frac{2}{3}=1 \)

To solve the equation by inserting \( + \) or \( - \) in each \( \bigcirc \), let's analyze the given equation: \[ \frac{13}{18} \bigcirc \frac{1}{9} \bigcirc \frac{1}{2} \bigcirc \frac{2}{3} = 1 \] **Step 1: Convert Fractions to Common Denominator** First, express all fractions with a common denominator of 18: \[ \frac{13}{18}, \quad \frac{1}{9} = \frac{2}{18}, \quad \frac{1}{2} = \frac{9}{18}, \quad \frac{2}{3} = \frac{12}{18} \] So the equation becomes: \[ \frac{13}{18} \bigcirc \frac{2}{18} \bigcirc \frac{9}{18} \bigcirc \frac{12}{18} = 1 \] **Step 2: Simplify the Equation** Multiply the entire equation by 18 to eliminate the denominators: \[ 13 \bigcirc 2 \bigcirc 9 \bigcirc 12 = 18 \] **Step 3: Determine the Operations** We need to determine where to place \( + \) or \( - \) to satisfy the equation: \[ 13 + 2 - 9 + 12 = 18 \] **Verification:** \[ 13 + 2 = 15 \\ 15 - 9 = 6 \\ 6 + 12 = 18 \] **Conclusion:** The correct placement of the operations is: \[ \frac{13}{18} + \frac{1}{9} - \frac{1}{2} + \frac{2}{3} = 1 \] **Final Answer:** \[ \frac{13}{18} + \frac{1}{9} - \frac{1}{2} + \frac{2}{3} = 1 \]