Why does 30+(-8)+(-6) equal 16? i'm so confused on this one

Af jewelry box is in the shape of a rectangular prism with an area of 528 cube inches. the length of the box is 12 inches and the height is 5 1/2 inches. what is the width of the jewelry box

According to the 2008 u.s. census, california had a population of approximately 4 × 10^7 people and florida had a population of approximately 2 × 10^7 people. which of the following is true? a. the population of california was approximately two times the population of florida. b. the population of florida was approximately twenty times the population of california. c. the population of florida was approximately two times the population of california. d. the population of california was approximately twenty times the population of florida.

Which set of side lengths form a right side? a) 3ft,6ft,5ft b)50 in,48in,14in c)53m,48m,24m d)8cm,17cm,14cm