The expression f о g = H is identical to f(g(x)) = H. In other words, when you put the function g(x) in the "x" position of the f(x) function, it should look like the H(x) function.
If g(x) = 9x + 2, put the entire function in for "x" in f(x) = |x|. Once you do this, you get the function f(g(x)) = |9x + 2|.
2.0² * π = 12.56637... 12.56637... * 9.6 = 120.6371579... 120.6371579.. / π = 38.4 √38.4 = 6.196773354... --> the radius of circle A dialated by 9.6 = 6.2 cm