If i have one mccookie, and i add 89 mccookies, and i split 78 of those mccookies into 1/4, how many mccookie pieces do i have?

89 + 1 = 90

Then take 78 (remember to add the 12 you have left over to your final answer!)

78 x 4 (because you now have four pieces for every one cookie you previously had)

Now you have 312 cookie pieces. Add back in the 12, and you have your

I have 324 McCookie pieces.