What is the answer ?

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)

Could somebody me with this radical simplification?

The? half-life of a radioactive substance is 20 years. if you start with some amount of this? substance, what fraction will remain in 120 ? years