Answer:
9 ( 2x - 1 )
Explanation:
→ Look for the HCF of the whole numbers
HCF of 18 and 9 is 9
→ Put 9 outside the brackets
9 ( ? - ? )
→ Perform the calculation 18x ÷ 9 to determine the first question mark
18x ÷ 9 = 2x ⇔ 9 ( 2x - ? )
→ Perform the calculation 9 ÷ 9 to determine the second question mark
9 ÷ 9 = 1 ⇔ 9 ( 2x - 1 )