AP Chem problem help

<p>First of all, let me say there was I time I thought I was smart, but once I saw this site and all the perfect or near-perfect scores I really don't think I have much of a chance getting into a top 25 school. It seems all of you must have IQs in the 140 range, and because a number of you take AP chem I was wondering if you could help me out. I am okay at chem, I have around an 85 in the course, which is around the highest in the class, and I expect to get a 5 on the AP, but I have been having problems with solubility.</p>

<ol>
<li>Calculate the solubility of silver phosphate (Ag3PO4) (Ksp=1.8 x 10^-18) in a 10.0 M HNO3 solution. HINT: the answer is 3.10 mol/L, but show how the problem is solved.</li>
<li> Caculate ACCURATELY the solubility of silver phosphate (Ag3PO4) (Ksp = 1.8 x 10^-18) in pure water. HINT: The actual solubility of silver phosphate is greater than the value caculated in #1 because the reaction of phosphate with water lowers the phosphate concentration and shifts the equilibrium to the right.</li>
</ol>

<p>I am close to getting the first one, but the second problem is killing me. I have two equilibrium expressions (the dissociation of silver phospate and the protonation of phosphate to form hydrogen phosphate), but I have FOUR unknowns. All you guys who got 5's or are planning to, please help me out. Thanks.</p>