First, two thirds is greater than zero, so its absolute value is equal to two thirds, and zero is less than two thirds. So the absolute value of 0 is less than two thirds-the absolute value of 7 is equal to 7, and the absolute value of 7 is equal to 7, so the absolute value of -7 is equal to the absolute value of 7.

The absolute value of a number is greater than or equal to zero, so if the absolute value of -a is equal to -a, (-a) should be greater than or equal to zero, and a is less than or equal to zero when solving inequality.

The essence of absolute value is not well grasped.