Let us assume the common ratio = x
Then from the given question we can write
7x + 2x = 450
9x = 450
x = 450/9
= 50
Then the quantity 450 grams can be divided in the ratio of 7 : 2 by = 7x:2x
= (7 * 50) : (2 * 50)
= 350:100
I hope this is the answer you were looking for and the procedure for finding the answer is also absolutely clear to you.