formula on google sheets

[kokopoof]

what is the formula on google sheets for :

I have 3 columns A,B,C

highlight if sum of column a and b doesn't equal column c.

 

[Joe4]

I do not use Google Sheets myself, but in Excel you would use Conditional Formatting to do this.
It looks like Google Sheets does have its own version of Conditional Formatting too, as shown here: Use conditional formatting rules in Google Sheets - Computer - Google Docs Editors Help