Question 874609
r(x)=3x



r(s(x))=3*( s(x) ) ... replace EVERY x with s(x)



r(s(x))=3*( x^3 - 6 ) ... replace s(x) on the right side with x^3 - 6



r(s(x))=3x^3 - 18 ... distribute (not always necessary and you can stop on the line above)