Chemistry amount of substance question

950 mg of impure calcium carbonate tablet was crushed. 50.0 cm3 of 1.00 mol dm-3 hydrochloric acid, an excess, was then added. After the tablet had reacted, the mixture was transferred to a volumetric flask. The volume was made up to exactly 100 cm3 with distilled water. 10.0 cm3 of this solution was titrated with 11.1 cm3 of 0.300 mol dm-3 sodium hydroxide solution.
Calculate the percentage of CaCO3 by mass in the tablet.

950 mg of impure calcium carbonate tablet was crushed. 50.0 cm3 of 1.00 mol dm-3 hydrochloric acid, an excess, was then added. After the tablet had reacted, the mixture was transferred to a volumetric flask. The volume was made up to exactly 100 cm3 with distilled water. 10.0 cm3 of this solution was titrated with 11.1 cm3 of 0.300 mol dm-3 sodium hydroxide solution.
Calculate the percentage of CaCO3 by mass in the tablet.

Are you familiar with what a back titration is?

I wasn’t but I watched a couple videos and i think it’s going better now

It’s good you now know what a back titration is and hopefully now have an idea as to what the strategy to solve calculations involving them is.
What I can’t help but notice about your questions of late is that they seem to involve things like diluting the solution and taking portions so you either have to adjust the concentrations to account for dilutions and/or account for portioning to know exactly how much of your analyte reacts.
If you can re-attempt these questions, that would be good. If you still are struggling to understand them, I’m very happy to talk you through them. I think it’d help a lot if I or Charco gave you hints and guided you through some of these problems.