Find the size of unknown number​

Which of the following is the best first step in solving the equation below? 4+2㏒³x=17

Which equation can be used to measure the density of water in a spherical water tank? let w represent the number of water particles within the region.

6. sarah saved $12.75 every week for a number of weeks, w. she received an additional $25 during the last week in which she saved money. write and solve an equation to find the number of weeks, w, for which sarah had saved money if she has $114.25 now.