The page is 12 inches wide. He wants to center the photo that is 3 1/2 inches wide. So, you do 12 - 3 1/2 (3.5), which equals 8.5. Then, because the page has 2 sides (obviously), you do 8.5 ÷ 2, so your answer is 4.25 (4 1/4) :)
P.S you are not stupid :)
Hi! So when you are dividing or multiplying a decimal by 10, it becomes a lot easier than it looks. If you divide by 10, you move the decimal to the left one space. If you multiply the decimal by 10, you move the decimal to the right one space. Because you are diving 12.5 by 10, you move the decimal to the left one space, which then becomes 1.25. So, Lauren has run 1.25 miles. If you want to double check, you can multiply 1.25 by 10, which comes out to 12.5. Your answer is 1.25! Hope this helps!!