How can I solve this using equations?

Question

A gym owner has some indigo weights and some green weights. The indigo weights are 9 kilograms each, and the green weights are 2 kilograms each. The owner has 9 weights, and they weigh 32 kilograms in all. How many of each color weight does he have?

Answer 1

Let x = number of indigo weights

     y = number of green weights

 

x + y = 9

      9x + 2y = 32

 

Multiply the first equation by -2:  -2x -2y = -18

                                                9x + 2y = 32

 

Add the equations:  7x = 14

 

                            So, x = 2 and  y = 7