Aa3+2=aaa cc6+6=cbb (ab|c) -> s57-> e73-> s47-> e57-> s43-> w26-> s18-> ? !

The complete question says: 
"Mark Atilius was expecting news from his friends with whom he agreed to reveal the great secret pyramids and spent his time at a nearby inn when he caught the attention of the Egyptian sitting beside him. He was even more surprised when he talked to him.
- You're Mark Atilius, are not you? she smiled - My name is Nefertari and I have a message for you from my grandmother. You should go right away if you want to get Pharaoh's belt you've been looking for all this time.
And he passed on the parchment he had just read.

AA3 + 2 = AAA
CC6 + 6 = CBB
(AB | C) -> S57 -> E73-> S47-> E57-> S43-> W26-> S18->?
Task: Find out the coordinates where Mark should come. "

The parchment indicates the starting position (AB, C) and the steps to make in which direction. 

In order to find the starting position, you need to find a three digits number, with the first two digits equal to each other and the last equal to 3, that summed to 2 gives you a three equal digits number.
Since 3 + 2 = 5, we can say A = 5, in fact 553 + 2 = 555.

Making a similar reasoning to solve the second line, since 6 + 6 = 12, which gives you B = 2 and C = 1, in fact 116 + 6 = 122.

Therefore the starting position is (52, 1).
Now, sum all the steps in the vertical direction:
S57 + S47 + S43 + S18 = S165

Now, do the same thing for the horizontal direction, remembering that towards the east the values will be positive, while towards the west the values will be negative:
E73 + E57 + W26 = 73 + 57 - 26 = 104, which being positive will be E104.

Last, apply these steps to the starting position:
(52, 1) moving S165 and E104 
(52 + 104, 1 - 165)
(156, -164)

Mark's final position will be (156, -164)