[18 – (10 – 6)] + 1

[18 – (10 – 6)] + 1  

 

First get rid of the unneccesary paranthesis:

 

18 – (10 – 6) + 1      

 

 

 

 

 

 

EITHER: Remember that -(a - b) = b - a

 

18 + 6 - 10 + 1 = 15

 

 

 

 

OR: Solve the usual way, be VERY carful so you avoid carless mistakes based on multiple minus signs:

 

18 – (10 – 6) + 1  = 18 - 4 + 1 = 15