If five arithmetic means are inserted between -9 and 9 what is the third mean?

Jack did 3/5 of all problems on his weekend homework before sunday. on sunday he solved 1/3 of what was left and the last 4 problems. how many problems were assigned for the weekend?

Find the roots of the polynomial function f(x) = x^3 + 2x^2 + x

Which describes the difference between the graph of f(x)=x^2 and g(x)=-(x^2-2)