Mathematics: Tell me about the quantitative relationship reflected in the following sentence, and be complete!

/kloc-the water consumption in October is 20% less than that in September;

If the water consumption in September is X, the water consumption in 10 is y= x( 1-20%).

There are 20% more people in art group than in dance group.

Let the number of people in the art group be y and the number of people in the dance group be x, then y=x( 1+20%).

Price reduction 15%

Let the price before the price reduction be X and the price after the price reduction be y=x( 1- 15%).

In 2003, it increased by 13% compared with 2002.

Let the output in 2002 be X and the output in 2003 be y=x( 1+ 13%).