Add:
14x + 10y – 12xy – 13, 18 – 7x – 10y + 8xy, 4xy

Dear Student

When term have the same algebraic factors, they are like terms. Then, we have to add the like terms
= 14x + 10y–12xy–13 + (18–7x–10y + 8xy) + 4xy
= 14x + 10y–12xy–13 + 18–7x–10y + 8xy + 4xy
= 14x–7x + 10y–10y–12xy + 8xy + 4xy–13 + 18
= x (14 - 7) + y (10 - 10) + xy(-12 + 8 + 4) + (-13 + 18)
= x (7) + y (0) + xy(0) + (5)
= 7x + 5

Thanks