Answer: 4 is 12 and 5 is 18
Step-by-step explanation: The midpoint of a line is the exact middle of the line. In other words, it splits the line into two equal parts.
From a formulaic standpoint, this looks like
AC = CB
And if we plug in the values it looks like this
AC = 12, so 12 = CB.
For the next problem,
AC + CB = AB
AC = 9, and since AC = CB, CB = 9 also.
So, once again just put the numbers in for the letters and you get
9 + 9 = 18