So we know that in all the seashells will be 40.
The ratio of ORANGE to PINK shells is 3:7.
Now we know that right now the sum is 10 seashells. To find the ratio of ORANGE to PINK seashells in a ration that has a sum of 40, we have to divide 40 seashells by 10 seashells (which is 4) and multiply it by both numbers (3 and 7).
3:7 is equal to 3x4:7x4 ---------> 12:28
Now we have to find how many orange seashells there are and we know that there are 12 orange seashells. :)
