Finding x and y in Pt(NH3)xCly
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For 8:  For every mole of acid added, it reacts with a mole of the base included in the Pt(NH3)xCly, which is the ammonia.  So you can figure out how many moles of ammonia have reacted, and compare this with the moles of salt you started with.

For 9: For every mole of AgCl you have formed, you have used up one mole of Cl from the Pt(NH3)xCly.  So you can figure out how many moles of Cl you have captured, and compare this with the moles of salt you started with.