Answer:
![SM=SA+AM](https://img.qammunity.org/2020/formulas/mathematics/high-school/ugeren42sgpzbq9s8zpezja72biyipm5mr.png)
![SA=AM](https://img.qammunity.org/2020/formulas/mathematics/high-school/d5nf2zphxwsd36ahwzz7ls6k5yqbmf8dtl.png)
Explanation:
see the attached figure to better understand the problem
we know that
The points S,A and M are collinear because they lie on a straight line. Using addition of segments we get
![SM=SA+AM](https://img.qammunity.org/2020/formulas/mathematics/high-school/ugeren42sgpzbq9s8zpezja72biyipm5mr.png)
The midpoint of a line segment divides the line segment into two congruent parts
If A is the midpoint of SM
then
![SA=AM](https://img.qammunity.org/2020/formulas/mathematics/high-school/d5nf2zphxwsd36ahwzz7ls6k5yqbmf8dtl.png)
therefore
The equations that satisfy the fact are
![SM=SA+AM](https://img.qammunity.org/2020/formulas/mathematics/high-school/ugeren42sgpzbq9s8zpezja72biyipm5mr.png)
![SA=AM](https://img.qammunity.org/2020/formulas/mathematics/high-school/d5nf2zphxwsd36ahwzz7ls6k5yqbmf8dtl.png)