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Answer:
![\huge\boxed{SM = 12}](https://img.qammunity.org/2021/formulas/mathematics/high-school/v0n487mljt947mimmg9xi971k82y90cexk.png)
SM = 2x + 6
MT = 3x + 3
M is the midpoint of SM
Write an expression to represent the length of ST:
ST = SM + MT
ST = 2x + 6 + 3x + 3
Combine like terms:
ST = 5x + 9
Since ST = 2(SM), set up another equation:
5x + 9 = 2(2x + 6)
5x + 9 = 4x + 12
Isolate the "x" variable:
5x - 4x = 12 - 9
x = 3.
Substitute in this value of "x" into the equation for SM:
2(3) + 6 = 12.