X = 32.
117 + 31 = 148.
180 - 148 = 32. (All angles in a triangle add up to 180 degrees)
To see how they are related, let us solve the two equations.
FIRST EQUATION
![m + 5 = 72](https://tex.z-dn.net/?f=m%20%2B%205%20%3D%2072)
![\rightarrow \: m = 72 - 5](https://tex.z-dn.net/?f=%20%5Crightarrow%20%5C%3A%20m%20%3D%2072%20-%205)
![\rightarrow \: m = 67](https://tex.z-dn.net/?f=%20%5Crightarrow%20%5C%3A%20m%20%3D%2067)
SECOND EQUATION
![m + 72 = 5](https://tex.z-dn.net/?f=m%20%2B%2072%20%3D%205)
![\rightarrow \: m = 5 - 72](https://tex.z-dn.net/?f=%20%5Crightarrow%20%5C%3A%20m%20%3D%205%20-%2072)
![\rightarrow \: m = - 67](https://tex.z-dn.net/?f=%20%5Crightarrow%20%5C%3A%20m%20%3D%20-%2067)
Hence the solutions to the two equations are ADDITIVE INVERSE of each other.
The common difference is essentially what u need to add to one number in the sequence to get the next
So previous number + common difference = next number after that
The common difference would be -8