Question 25723
x + 3 = 9  
Subtracting 3 from both sides
X+3 -3 = 9-3
X = 6

  x - 3 = 3   
Adding 3 on both sides
X-3 +3 = 3+3
X = 6
  All we did was perform simple mathematical operations to get the value of X

In both cases, the value of X equals 6.
Thus we can say that both the equations are equal since both evaluate to the same answer X = 6.