How do you write 3/10 as decimal point

Can someone me i’m confused. will give brainliest and a whole bunch of points

The area of a rectangle is 10 cm^2. one side of the rectangle is x cm. express the perimeter of the rectangle in terms of x and show that this rectangle cannot have a perimeter of 12 cm. the perimeter of the rectangle in terms of x is __ cm

If value of cos330° is √3/2 then find tan165°.