The statement tells us two important things
1. The store sells 108 rattles
2. For every two green rattles the toy shop sells, it sells seven yellow rattles
However, we are asked to halal the proportion of yellow rattles out of the 108 rattles sold.
For this, we must take into account that 2 green rattles correspond to the sale of 7 yellow rattles, that is to say, always the sum of these is sold.
Now, we divide 108 by 9
i.e. 12 times this ratio was sold, to know how many of these 12 groups are yellow, we multiply them by 7.
in conclusion, the toy store sold 84 yellow rattles.