Hey there!!
Let's take the measurement of bracelet as x inches
Then, the measurement of the necklace would be 2x inches
The total measure = 28.5 inches
Hence, x + 2x would be equal to 28.5 inches
x + 2x = 28.5
... 3x = 28.5
Divide by 3 on both sides
... x = 9.5
Hence, the length of the bracelet = 9.5 inches
Then, the length of the necklace would be 9.5 × 2
Hence, the length of the necklace = 19 inches
Hope my answer helps!!