Write + or - in each \( \bigcirc \) to make each equation true. (a) \( \frac{13}{18} \bigcirc \frac{1}{9} \bigcirc \frac{1}{2} \bigcirc \frac{2}{3}=1 \) (b) \( \frac{3}{4} \bigcirc \frac{13}{24} \bigcirc \frac{5}{8} \bigcirc \frac{1}{6}=1 \)

Let's solve each equation step-by-step! (a) \( \frac{13}{18} \bigcirc \frac{1}{9} \bigcirc \frac{1}{2} \bigcirc \frac{2}{3}=1 \) We can try combining \( + \) and \( - \) operations. After testing various combinations, we find: \[ \frac{13}{18} - \frac{1}{9} + \frac{1}{2} - \frac{2}{3} = 1 \] Rewriting it, we find a common denominator of 18: \[ \frac{13}{18} - \frac{2}{18} + \frac{9}{18} - \frac{12}{18} = 1 \] Adding those fractions, we have: \[ \frac{13 - 2 + 9 - 12}{18} = \frac{8}{18} = \frac{4}{9} \] This doesn't yield 1. Upon adjusting our calculations again and testing combinations, we conclude: \[ \frac{13}{18} + \frac{1}{9} - \frac{1}{2} + \frac{2}{3} \] When working this out: \[ \frac{13}{18} + \frac{2}{18} - \frac{9}{18} + \frac{12}{18} = 1 \] The successful operation combination is: \[ + - + \] (b) \( \frac{3}{4} \bigcirc \frac{13}{24} \bigcirc \frac{5}{8} \bigcirc \frac{1}{6}=1 \) To solve this, we again test various combinations. After some attempts, we arrive at the correct combination: \[ \frac{3}{4} + \frac{13}{24} - \frac{5}{8} - \frac{1}{6}=1 \] Calculating with a common denominator of 24 gives us: \[ \frac{18}{24} + \frac{13}{24} - \frac{15}{24} - \frac{4}{24} = \frac{18 + 13 - 15 - 4}{24} = \frac{12}{24} = \frac{1}{2} \] This doesn't yield 1 either. Finally, by testing again: \[ \frac{3}{4} - \frac{13}{24} + \frac{5}{8} + \frac{1}{6} \] Reorganizing with a consistent denominator: \[ \frac{18}{24} - \frac{13}{24} + \frac{15}{24} + \frac{4}{24} = \frac{24}{24} = 1 \] So the final operations for this are: \[ - + + \] In summary, **a)** \( + - + \) and **b)** \( - + + \). Happy equation solving!