9/19 - 1,251 + 10/19 + 1,251

Lời giải:

\(\frac{9}{{19}} - 1,251 + \frac{{10}}{{19}} + 1,251\)

\( = \left( {\frac{9}{{19}} + \frac{{10}}{{19}}} \right) + ( - 1,251 + 1,251)\)

= 1 + 0 = 1;