The like terms are 5a and -3a. Also, 8 and 11 are like terms
8 and 11 are like terms because they both are constants and don't have a variable.
5a and 3a are like terms because they both have the variable a in common.
you would combine these like terms
5a + 8 - 3a + 11
(5a - 3a) + (8 + 11)
2a + 19
Hope this helps :)