-13.24 + b + 4.9 + 8.24 + (-4.9) = -13.24 + b + 4.9 + 8.24 - 4.9 = -13.24 + 8.24 + b + 4.9 - 4.9 = -5 + b
Если $b = 3\frac{4}{9} = \frac{31}{9} = 3.444...$, то -5 + 3.444... = -1.555... = -1$\frac{5}{9}$
Ответ: -5 + b; -1$\frac{5}{9}$
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