Mark gave 21 tadpoles to his threes friends. Mark gave twice as many tadpoles to David as his did Chris. George received twice as many tadpoles as David. How many tadpoles did each friend receive?

So Chris would have 1x, David would have 2x, and George would have 4x, so add them together and get 7x, so you divide by 7 and that's 3=x so Chris would have 3, David would have 6, and George would have 12

First you need to fined what numbers you need to use.

next you need to do 21*3=63

(if you need) divide 3:63=21

so that is how you know if its right