6, 35, 20, 6, 20, 18, 7, 20, 28, 40, find the standard deviation

Write each fraction as an equivalent fraction with a denominator of 120then write the original fractions in order from samllest to largest

The sum of two numbers is 86, and their difference is 20. find the two numbers

Me, the vertices of quadrilateral coat are c(2,0), o(7,0), a(7,2) and t(2,2). prove that coat is a rectangle.