This is an illustration of multiplicative property of inequality.
According to the property if two values are equal, and the same number is multiplied to the both sides of the equation, the two values remain equal.
In given case
MN= 2AB
Both sides are multiplied by 3, and we get
3MN = 6AB
Since same number is being multiplied, the result will be equal.
So, correct answer is Multiplication property of equality