Find the lcm of 18 and 48. insert all the prime numbers in the corresponding boxes below

What you're discussing here is prime factorization (or turning a number into the multiples of its prime numbers).  18 becomes 2*3*3.  48 becomes 2*2*2*2*3. They share one 2 and one 3 in those prime factors.  Which is why 6 is their least common multiple (or LCM).  Because, 2*3 = 6.

Lcm=least common multiplule

factor
18=2*3*3
48=2*2*2*2*3

we need to have at least two 3's and four 2's
lcm=2*2*2*2*3*3=144