Is this translation done correctly? How do you know?

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

The width of a rectangle is 20 units. can the perimeter p of the rectangle be 64 units when its length x is 11 units? no, because p = 2x + 2(20) no, because p ≠ 2x + 2(20) yes, because p ≠ 2x + 2(20) yes, because p = 2x + 2(20)

What is the value of m in the equation 1/2 m - 3/4n=16 when n=8