What should be subtracted from (186+215+46-170) to get 188?

Expression = (186 + 215 + 46 − 170)
Required result = 188

Formula / Concept used:
Number to be subtracted = Value of expression − Required result

Solution:
First calculate the expression:
186 + 215 = 401
401 + 46 = 447
447 − 170 = 277

Now find the number to be subtracted:
277 − 188 = 89