-- Cut the sheet in half.
-- Put one half-sheet on top of the other half-sheet.
Cut the stack of 2 halves in half.
-- Put one stack of two quarter-sheets on top of the other stack of quarter-sheets.
Cut the stack of 4 quarters in half.
Now you have eight one-eighth sheets.
Three cuts.
Taking Sam (3 x 5) = 15 minutes, plus a few seconds for set-up between cuts.
We know that 5 fits entirely into our number three times, and then there's a remainder of 4.
If 5 fits three times exactly, it means that our number is at least 15 (5x3).
From here, we have a remainder of 4, which leads to 15+4=19
Answer:
n = 17

Step-by-step explanation:

n · 170 = 34 · 85
170y = 2890
170y ÷ 170 = 2890 ÷ 170
y = 17