Each year the necklace gains 2.5% of its own value. To write a percentage as a decimal number, we just divide it by 100.

Since each year the necklace gains 2.5% of its own value, this means that each year we multiply the previous price by 100% plus this rate, which is

then, the value after one year is given by

and every year that passes, we multiply by this factor

The amount of times we multiply, is the amount of years that passed. Since we want to know the price after 10 years, the calculation is

The price after 10 years will be $1062.47.