Let us take an equation x+2y=5 .....(1)
Put x=1 in eqn (1)
⇒y=2
So,x=1,y=2 is a solution of the equation
Multiplying both sides of equation 1() by 3, we get
3x+6y=15
Put x=1,y=2 in LHS
LHS =3×1+6×2=15= RHS
Hence, on multiplying an equation by a non-zero number , the solution remains same.