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Hi !
Since all the reactions seems to be complete, you can use the sample stoichiometry calculation.

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First, you have to make sure that the reactions are balanced. wich means that the proportion of atoms are the same on each side of the reaction. You will also need at times to write them first.

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For example, in #1, they give a reaction and an amount of iron (Fe). Considering that the oxygen is on a saturated quantity. You can then transform the amount in mole (with the molar mass/molecular weight) and do the calculations.
I'll let you first try by yourself and you have any other questions, feel free to ask them.
Have a nice day !