Figure out which of the variables are like terms, i.e which variables are the same and can be combined together? 7h + 5k + h - 7k Here we've added h to 7h: 8h + 5k - 7k And then, taken 7k away from 5k: 8h + (-2k) However, the simplest way of writing this is: 8h - 2k adding a negative number is the same as taking away the positive.