List all of the numbers between 20 and 30 that are prime

George is 187 cm tall. his son, ralph, is 142 cm tall. who casts the longer shadow. george when the sun is 65° above the horizon, or ralph when the sun is 56° above the horizon? how much longer? (nearest centimeter)

The number of branches on a tree demonstrates the fibonacci sequence. how many branches would there be on the next two levels of this tree? 13 | | | m branches

Aquadratic equation in standard from is written ax^2= bx+c, where a, b and c are real numbers and a is not zero?