Answer:
k = 20
Step-by-step explanation:
Expressing 18, 36 and 54 as a product of their prime factors
18 = 2 × 3 × 3 = 2 × 3²
36 = 2 × 2 × 3 × 3 = 2² × 3²
54 = 2 × 3 × 3 × 3 = 2 × 3³
The common prime factors are 2 and 3²
HCF = 2 × 3² = 2 × 9 = 18
Thus
k - 2 = 18 ( add 2 to both sides )
k = 20
