What is 645 rounded to the nearest tenth

At the beginning of the day, stock xyz opened at $6.12. at the end of the day, it closed at $6.88. what is the rate of change of stock xyz? a. 1.17% b. 11.0% c. 12.4% d. 81.5%

Suppose y varies directly with x. write a direct variation equation that relates x and y. then find the value of y when x=12 y=7 when x=3

Why can't my rank go i have 1723 points, but my rank is only at ambitious, which is only 250 points! like, (p.s. i know this isn't related to math, but i just don't know why it's doing this and i would really appreciate if someone could tell me whats going on with this)