Please help asap 18 pts brainliest to right/best answer

Find the Greatest Common Factor (GCF)
GCF = 3x
Factor out the GCF (Write the GCF first. Then, in parentheses, divide each term by the GCF.)
3x(3x^2/3x + 21x/3x)
Simplify each term in parenthesis
3x(x + 7)