What is the solution to the equation 5x+4=7

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.

What is the range? can’t seem to find it out

Can someone tell me if this is perpendicular? !