9.37.3 Can you answer these questions?

9.37.3.1 How can I remove gaps in histogram comparing graphs?

https://tex.stackexchange.com/landing/r/digest?cta=question&id=687451

If possible I want to draw following simple histogram, where there is no much gap in between. 
When I try (original code is taken from: PGFPlots histogram not showing all series): 
\documentclass{... 
[pgfplots] [gap]
 

asked by alper https://tex.stackexchange.com/landing/r/digest?cta=user&id=127048 Score of 1

9.37.3.2 Combining tabularray and aligned environment

https://tex.stackexchange.com/landing/r/digest?cta=question&id=687565

I am trying to get the following to work 
MWE: 
\documentclass{article} 
\usepackage{tabularray} 
\usepackage{mathtools} 
\newcommand*{\tn}[1]{\textnormal{#1}} 
\newcommand*{\Utevolv}{\ensuremath{\hat{\... 
[amsmath] [mathtools] [tabularray]
 

asked by Martin Dagleish https://tex.stackexchange.com/landing/r/digest?cta=user&id=228238 Score of 1

answered by Martin Dagleish https://tex.stackexchange.com/landing/r/digest?cta=user&id=228238 Score of 0

9.37.3.3 Theorem style Format

https://tex.stackexchange.com/landing/r/digest?cta=question&id=687560

I am curious how I can make a similar format of definition and theorem as shown in the picture? Moreover, can I separate two kinds of definition or theorem format so that whenever I see fit, I use the ... 
[theorems]
 

asked by Andrew Leung https://tex.stackexchange.com/landing/r/digest?cta=user&id=296730 Score of 1