The answer is 574, its very easy, all u have to do is this.
1st grader has 7, 4th grader has 82 * as much as 1st grader, 1st grader has 7 so 82 * 7 = 574
here is your multi step problem, 82 * 7 = 574 and that's how many words the 4th grader has on their book.