In[]:=
​​Needs["Notation`"]​​
In[]:=
circlePlus[a_,b_]:=2a+b
In[]:=
circlePlus[5,6]
Out[]=
16
In[]:=
Notation
x_⊕y_
⟺
circlePlus[x_,y_]

In[]:=
5⊕6
Out[]=
16
In[]:=
6⊕4
Out[]=
16
In[]:=
10⊕1
Out[]=
21
In[]:=
6⊕10
Out[]=
22
In[]:=
Solve[7⊕x14,x]
Out[]=
{{x0}}
In[]:=
Solve[x⊕323,x]
Out[]=
{{x10}}