What is the steps and answer to :

3x=y-20
-7x-y=40
Using the elimination method?

Find all the angles that satisfy the equation cos(θ)=32

The roof of a farm silo is the shape of a hemisphere and is made of sheet tin. if the diameter of the silo is 126.5 feet, how much sheet tin is needed to make the roof? (use π = 3.1416.)

Enter the amplitude of the function. f(x)=3cosx