What mass of 20% hydrochloric acid is required to completely dissolve a marble figurine (no impurities) weighing 50 g?

we compose the equation for the dissolution of marble:
2HCl + CaCO3 = CaCl2 + H2O + CO2.
1) Determine the molar mass of marble according to the periodic table: 24 + 12 + 16 * 3 = 84.
2) Find the amount of the marble substance. For this, the mass of marble given in the condition of the problem is divided by the molar mass: 50/84 = 0.6 mol.
3) According to the reaction equation, there are two moles of hydrochloric acid per mole of marble. This means that the amount of hydrochloric acid substance is: 0.6 / 2 = 0.3 mol.
4) The mass of hydrochloric acid in its solution is equal to: 0.3 * 36.5 = 10.95 g.
5) The mass of the hydrochloric acid solution is: 10.95 * 100/20 = 54.75 g – the answer.