The Combination Lock

The eerie room’s door was not outfitted with a normal lock. Instead, it depended on a dial combination mechanism. The silver wheel is slightly worn out but you can still distinguish the marks and numbers going from 00 to 39. Figuring out the combination should be simple, right? You just need to spin the dial until you hear a click.

After a few minutes of slowly turning the wheel, however, you give up. The lock is too sensitive to fake a tumbler into falling in, so you know you need to get the precise position. Trying every single combination would take days, by which point there would be two corpses in the room. You need to try a different way.

Being up and close to the wall you notice the presence of dark stains around the dial. You would have dismissed them but their positioning seems too organised to be random. Looking closely, you see indentations in the cement within each stain and, shining your flashlight along the wall’s surface, you discover what they are. The indentations are letters, visible thanks to the contrast of the ink smudges! Their contents, however, seem to be riddles to obtain the right combination.

There are three clues and you can only assume that each one corresponds to one of the three sets of 2-digit numbers to the combination lock. The first clue consists of a bunch of lines of varying lengths and what looks to be an equation.

{[(6 ÷ 20) ÷ (15 + 8)] x 3 ÷ 9 + 13 - 5 + 12} ÷ [17 ÷ (7 ÷ 16)]

What is the 2-digit number?