Combination Hydration Equation

I need help.  I've committed to 30 loaves of bread for the Church sale on Saturday.  My plan was to pre-ferment a large quantity of high hydration dough-easier on the mixer--and use it to improve the smaller quantities of lower hydration dough.  Good plan, huh?  But...

Now I have a large batch of 87% hydration first dough, "x", and want to mix it with 55% hydration second dough, "y", to end up with a 60% hydration final dough, "z".  I've let my math skills get rusty, or maybe I'm just getting old, but I cannot quite set up the equation I need.

How many oz of "x" and how many of "y" are needed to yield 32 oz of "z"?

Help, O Wise Ones!!

Ju-Ju