Answer
298.5g
Work Step by Step
Total mass of first sample = 12.0 + 106.4 + 1.01 = 119.4 g
Mass of carbon in first sample = 12.0g
Ratio of carbon in first sample = $\frac{12.0}{119.4}$
Mass of carbon in second sample = 30 g
According to law of definite proportion the mass ratio of carbon should remain same in the new sample.
=> $\frac{mass\space of\space carbon\space in\space new\space sample}{total\space mass\space of\space new\space sample}$ = $\frac{12.0}{119.4}$
=> $\frac{30}{total\space mass\space of\space new\space sample}$ = $\frac{12.0}{119.4}$
=> Total mass of new sample = $30\times \frac{119.4}{12.0}$ = 298.5g
