What is 2.1 times 10^4 in standard form

Identify whether the figure has plane symmetry, symmetry about an axis, or neither.

Aline parallel to a triangle's side splits ab into lengths of x - 5 and x + 2. the other side, ac, is split into lengths of x and x + 12. what is the length of ac? a) 12 b) 24 c) 36 d)

Asquare picture with sides of 32 inches is to be mounted on a square mat with sides of 52 inches. find the area of the mat that will remain uncovered by the picture.