Starting with
80, 45, 35
divide each number by the first prime number, 2, as many times as needed until you arrive at 1. If it's not perfectly divisible by 2, leave it alone.
40, 45, 35 … … … 1 division by 2
20, 45, 35 … … … 2 divisions
10, 45, 35 … … … 3 divisions
5, 45, 35 … … … 4 divisions
We stop here, and take note that we divided by 2⁴.
Now continue with the next prime, 3.
5, 15, 35 … … … 1 division by 3
5, 5, 35 … … … 2 divisions
Stop; we've divided by 3².
Now with the next prime, 5.
1, 1, 7 … … … 1 division by 5
Stop; we've divided by 5¹.
The next prime is 7.
1, 1, 1 … … … 1 division by 7
Stop; we've divided by 7¹.
The division method then says that the LCM of 80, 45, and 35 is then
2⁴ × 3² × 5¹ × 7¹ = 16 × 9 × 5 × 7 = 5040