The mid point is quite easy to find on a calculator as the mid point is between two numbers.
For an example; finding the midpoint of 4 and 12 you may simply insert the equation : 4+12/2 which equals 8. Meaning your mid point is 8.
For your question; 125 + 12 = 137/2 = 68.5
The mid point of 125 and 12 is 68.5.
