To solve the expression step by step, we can compute each part individually.
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First part: \((18.51 + 19.88) / 2\) \[ \frac{18.51 + 19.88}{2} = \frac{38.39}{2} = 19.195 \]
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Second part: \((1.37 + 2.74) / 2\) \[ \frac{1.37 + 2.74}{2} = \frac{4.11}{2} = 2.055 \]
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Third part: \(2.06\) (this part remains as is since it’s already a single number).
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Fourth part: \((6.86 + 13.71) / 2\) \[ \frac{6.86 + 13.71}{2} = \frac{20.57}{2} = 10.285 \]
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Fifth part: \((15.00 + 30.00) / 2\) \[ \frac{15.00 + 30.00}{2} = \frac{45.00}{2} = 22.5 \]
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Sixth part: \((0 + 3.45) / 2\) \[ \frac{0 + 3.45}{2} = \frac{3.45}{2} = 1.725 \]
Now, we can add all these results together: \[ 19.195 + 2.055 + 2.06 + 10.285 + 22.5 + 1.725 \]
Calculating this step by step: \[ 19.195 + 2.055 = 21.25 \] \[ 21.25 + 2.06 = 23.31 \] \[ 23.31 + 10.285 = 33.595 \] \[ 33.595 + 22.5 = 56.095 \] \[ 56.095 + 1.725 = 57.82 \]
Therefore, the final result is: \[ \boxed{57.82} \]