Help help please I need help

Select all the correct answers. what is 221,000,000,000,000,000,000 expressed in scientific notation?

Given that y varies directly to the square root of (x + 1), and that y = 1 when x = 8,(a)express y in terms of .x,(b)find the value of y when x = 3,(c)find the value of x when y = 5.

Gabrielle's age is two times mikhail's age. the sum of their ages is 84. what is mikhail's age?