Answer: The required cost of the magazine is $10.
Step-by-step explanation: Given that Ryan bought 3 books and a magazine. He paid $30 and relieved $5 change and the magazine cost twice as much as each book.
We are to find the cost of the magazine.
Let x and y represents the cost of a book and the magazine respectively.
Then, according to the given information, we have

and

Substituting the value of y from equation (ii) in equation (i), we get

and from equation (ii), we get

Thus, the required cost of the magazine is $10.