Answer
Answers may vary, but two possible solutions are below.
20: $9g^2 + 20g+4 = (9g+2)(g+2)$
12: $9g^2 + 12g+4 = (3g+2)(3g+2)$
Work Step by Step
$9g^2+xg+4$
$(9g+2)(g+2) = 9g^2 +18g+2g+4 = 9g^2 + 20g+4$
$(3g+2)(3g+2) = 9g^2 +6g+6g+4 = 9g^2 + 12g+4$