4. в) $$7\frac{15}{19}⋅6\frac{4}{19}+4\frac{6}{19}$$

Решение:

$$7\frac{15}{19} \cdot 6\frac{4}{19}+4\frac{6}{19} = \frac{7 \cdot 19 + 15}{19} \cdot \frac{6 \cdot 19 + 4}{19} + \frac{4 \cdot 19 + 6}{19} = \frac{133 + 15}{19} \cdot \frac{114 + 4}{19} + \frac{76 + 6}{19} = \frac{148}{19} \cdot \frac{118}{19} + \frac{82}{19} = \frac{148 \cdot 118}{19 \cdot 19} + \frac{82}{19} = \frac{17464}{361} + \frac{82}{19} = \frac{17464}{361} + \frac{82 \cdot 19}{19 \cdot 19} = \frac{17464}{361} + \frac{1558}{361} = \frac{17464 + 1558}{361} = \frac{19022}{361} = 52\frac{290}{361}$$

Ответ: $$52\frac{290}{361}$$