During dinner time, Yves and his siblings ate 16/4 = <<16/4=4>>4 slices.
So the next day, there were still 16 - 4 = <<16-4=12>>12 slices left.
The next day, Yves ate 12/4 = <<12/4=3>>3 slices of pizza.
Thus, there were 12 - 3 = <<12-3=9>>9 slices left.
Then, his two siblings ate 2 x 2 = <<2*2=4>>4 slices of pizza.
Therefore, there were still 9 - 4 = <<9-4=5>>5 slices of pizza left.
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