It is given in the question that
A person is 185 cm tall and casts a shadow 145 cm long. A nearby tree casts a shadow which is 212 cm long.
And we have to find the height of the tree. Let it be x cm .
Now we use the ratio, which is

Now we need to get rid of the denominators, and for that we do cross multiplication. That is

Dividing both sides by 145

And that's the required height of the tree.