54+23+45++75+18+34+18+52+23+54+42+12:5

Let's break down the expression step by step.

First, let's add the numbers together:

54 + 23 + 45 + 75 + 18 + 34 + 18 + 52 + 23 + 54 + 42 + 12 = 54 + 23 = 77
77 + 45 = 122
122 + 75 = 197
197 + 18 = 215
215 + 34 = 249
249 + 18 = 267
267 + 52 = 319
319 + 23 = 342
342 + 54 = 396
396 + 42 = 438
438 + 12 = 450

Now, we will divide by 5:

450 ÷ 5 = 90

Thus, the final result of the entire calculation is 90.