I need to find the mid point of the equation but I am not sure what points I put into the equation, since I'm not given any coordinates

the assumption being that M is the midpoint of AC, if that's the case, then M cuts AC into two equal halves, namely then AM = MC
[tex]\bf \stackrel{AM}{x+5}=\stackrel{MC}{2x}\implies 5=x~\hfill \stackrel{AM~\hfill AM}{x+5\implies 5+5\implies 10}[/tex]