I need help with this is kinda hard

The sum of two numbers is 12 and their difference is 18 what are the two numbers

Tod does not have any cookies. david gives jeff 8 cookies. then he splits half of the cookies he has left with tod. david let’s c represent the number of cookies that he starts with. he finds the number of cookies that tod has is 1/2 the difference of c and 8. write an expression to represent the number of cookies that tod has.

Ineed i been stuck on this question since yesterday