def functions on advanced graphing

[compsystems]

Hello, I want to define two functions for the application advanced graphing from history view.

purge(X,Y);
from HOME V1(X,Y):=X-2*Y=7; V2(X,Y):=5*X-3*Y=2; returns Error: Invalid input

from CAS V1(X,Y):=X-2*Y=7; V2(X,Y):=5*X-3*Y=2; returns (X,Y)->false,(X,Y)->false
solve([V1(X,Y),V2(X,Y)],[X,Y]) returns [X,Y] ?

although pressing the SYMB button the definitions of the functions are well defined

How can I define or externally delete the variables of the applications?