diff --git a/2-ui/1-document/09-size-and-scroll/1-get-scroll-height-bottom/solution.md b/2-ui/1-document/09-size-and-scroll/1-get-scroll-height-bottom/solution.md
@@ -1,7 +1,7 @@
-The solution is:

```js
let scrollBottom = elem.scrollHeight - elem.scrollTop - elem.clientHeight;
```

-In other words: (full height) minus (scrolled out top part) minus (visible part) -- that's exactly the scrolled out bottom part.
diff --git a/2-ui/1-document/09-size-and-scroll/1-get-scroll-height-bottom/task.md b/2-ui/1-document/09-size-and-scroll/1-get-scroll-height-bottom/task.md
@@ -2,10 +2,10 @@ importance: 5

---

-# What's the scroll from the bottom?

-The `elem.scrollTop` property is the size of the scrolled out part from the top. How to get the size of the bottom scroll (let's call it `scrollBottom`)?

-Write the code that works for an arbitrary `elem`.

-P.S. Please check your code: if there's no scroll or the element is fully scrolled down, then it should return `0`.
diff --git a/2-ui/1-document/09-size-and-scroll/2-scrollbar-width/solution.md b/2-ui/1-document/09-size-and-scroll/2-scrollbar-width/solution.md
@@ -1,16 +1,16 @@
-To get the scrollbar width, we can create an element with the scroll, but without borders and paddings.

-Then the difference between its full width `offsetWidth` and the inner content area width `clientWidth` will be exactly the scrollbar:

```js run
-// create a div with the scroll
let div = document.createElement('div');

div.style.overflowY = 'scroll';
div.style.width = '50px';
div.style.height = '50px';

-// must put it in the document, otherwise sizes will be 0
document.body.append(div);
let scrollWidth = div.offsetWidth - div.clientWidth;


diff --git a/2-ui/1-document/09-size-and-scroll/4-put-ball-in-center/task.md b/2-ui/1-document/09-size-and-scroll/4-put-ball-in-center/task.md
@@ -2,19 +2,19 @@ importance: 5

---

-# Place the ball in the field center

-Here's how the source document looks:

[iframe src="source" edit link height=180]

-What are coordinates of the field center?

-Calculate them and use to place the ball into the center of the green field:

[iframe src="solution" height=180]

-- The element should be moved by JavaScript, not CSS.
-- The code should work with any ball size (`10`, `20`, `30` pixels) and any field size, not be bound to the given values.

-P.S. Sure, centering could be done with CSS, but here we want exactly JavaScript. Further we'll meet other topics and more complex situations when JavaScript must be used. Here we do a "warm-up".