Rounding decimals is like rounding whole numbers. 7.92 is closer to 8 right?. Because if you take out the decimal point it would be 792. And you rounded that to 800 now put the decimal point back which is 8.00= 8. do the same thing to 5.37 and you get 5. 8+5= 13 and that is your answer. Hope this helped
you need to know the mass of the jewelry box before you can know the volume but i can help you multiply th 15 and the 10 to get the mass most likely then divided what you have from 15 x 10 by the depth and you have your answer just be sure to round it off!