Step 1: Define variables
Let the original number of apples be $2x$, mangoes be $3x$, and oranges be $187 - 5x$ (since the total number of fruits is 187).
Step 2: Calculate remaining fruits after sales
Apples sold = 67 $\rightarrow$ Remaining apples = $2x - 67$.
Mangoes sold = 26 $\rightarrow$ Remaining mangoes = $3x - 26$.
Half of the oranges sold $\rightarrow$ Remaining oranges = $\frac{187 - 5x}{2}$.
Step 3: Apply the ratio condition
After sales, the ratio of remaining apples to remaining oranges is $1 : 2$:
\[\frac{2x - 67}{\frac{187 - 5x}{2}} = \frac{1}{2}.\]
Step 4: Solve for $x$
Cross-multiply to simplify:
\[2 \cdot (2x - 67) = 187 - 5x.\]
\[4x - 134 = 187 - 5x.\]
Combine like terms:
\[4x + 5x = 187 + 134 \quad \rightarrow \quad 9x = 321.\]
Calculate $x$:
\[x = 35.7 \quad \text{(round down to the nearest integer, } x = 35 \text{)}.\]
Step 5: Calculate the original number of each fruit
Apples = $2x = 2 \times 35 = 70$.
Mangoes = $3x = 3 \times 35 = 105$.
Oranges = $187 - 5x = 187 - (5 \times 35) = 187 - 175 = 12$.
Step 6: Calculate the number of fruits remaining after sales
Remaining apples = $70 - 67 = 3$.
Remaining mangoes = $105 - 26 = 79$.
Remaining oranges = $\frac{12}{2} = 6$.
Step 7: Calculate the total number of unsold fruits
\[\text{Total unsold fruits} = 3 + 79 + 6 = 88.\]
Conclusion: The total number of unsold fruits is 88.