Kate purchased a box of 36 pencils to donate to Mr. Brown's class, but not all pencils were used. The ratio of pencils that were used to the pencils that did not use is 7 to 5. How many pencils were left from the box of pencils Kate bought?

Answer:15Step-by-step explanation:The ratio of pencils that were used to the pencils that did not use is 7 to 5. So, let the number of pencils that were used = 7x and the number of pencils that did nor use = 5x. Hence, total number of pencils that Kate purchased is 7x + 5x = 36 ⇒ 12x = 36 ⇒ x = 3 Therefore, the number of pencils that left in the box was 5x = 15 . (Answer)