2. Решите уравнения: a) 7,7+x=2,54; б) -3\frac{7}{12}-x=2\frac{13}{15}.

а) 7.7 + x = 2.54

x = 2.54 - 7.7

x = -5.16

б) -3\frac{7}{12} - x = 2\frac{13}{15}

-x = 2\frac{13}{15} + 3\frac{7}{12}

-x = \frac{43}{15} + \frac{43}{12}

-x = \frac{43 \cdot 4}{15 \cdot 4} + \frac{43 \cdot 5}{12 \cdot 5}

-x = \frac{172}{60} + \frac{215}{60}

-x = \frac{387}{60}

-x = \frac{129}{20}

-x = 6\frac{9}{20}

x = -6\frac{9}{20}