Step 1: make seedlings in each row equal, means find out the common factors of each kind of seedlings:
42 pine seedlings: 2, 3, 6, 7, 14, 21
30 oak seedlings: 2, 3, 5, 6, 10, 15
Step2: the greatest number of those seedlings above is 6, and the answers are as follows:
1/ greatest number of each row is 6
2/ pine: 42/ 6= 7; oak: 30/ 6= 5
