Find the next number is the sequence

1, 2, 6, 21, 4, 0, ?

For one history test, keith had to answer 40 questions. of these 40 questions, keith answered 28 of them correctly. what percent did keith get on his history test? round your answer to the nearest tenth if necessary

Given the functions, f(x) = 2x^2 - 1 and g(x) = 5x, find f(g(x)) and g(f(

Which expression is equivalent to 64 - 9x^2?