Answer
a) 19.5 g
b) 72.9 g
Work Step by Step
a) Use the conversion:
$75.45\ g_{sample}\cdot\dfrac{25.8\ g_{CaCO_3}}{100.0\ g_{sample}}=19.5\ g_{CaCO_3}$
b) Use the conversion:
$18.8\ g_{CaCO_3}\cdot\dfrac{100.0\ g_{sample}}{25.8\ g_{CaCO_3}}=72.9\ g_{sample}$
