\[5\frac{1}{4} \cdot (12 - c) + 3\frac{1}{4} \cdot ( - c - 8) =\]
\[= \frac{21 \cdot 12}{4} - 5\frac{1}{4}c - 3\frac{1}{4}c - \frac{13 \cdot 8}{4} =\]
\[63 - 8\frac{2}{4}c - 26 = 37 - 8\frac{1}{2}c\]
\[c = - 0,4:\]
\[37 - 8\frac{1}{2}c = 37 - 8\frac{1}{2} \cdot ( - 0,4) =\]
\[= 37 + \frac{17 \cdot 4}{2 \cdot 10} = 37 + \frac{34}{10} =\]
\(= 37 + 3,4 = 40,4.\)