15. (1 - 3) * 4

1. Convert mixed number to improper fraction: $$1 \frac{11}{16} = \frac{27}{16}$$.
2. Subtract fractions: $$\frac{27}{16} - 3 \frac{3}{8} = \frac{27}{16} - \frac{27}{8} = \frac{27 - 54}{16} = -\frac{27}{16}$$.
3. Multiply by 4: $$-\frac{27}{16} * 4 = -\frac{27}{4}$$.