Answer:
12
Step-by-step explanation:
You set up cross multiplication 3/4 x 9/x, you go 4x9=36 divided by 3 equals 12
18x^3 = 6x^3 * 1
30x^5 = 6x^3 * 5x^2
So GCF = 6x^3
Answer
6x^3