The Four Types of Sentence

Letter 1

Explanation

1.  Simple Sentences 
Contains 1 independent clause (IC).
One IC:
We hope to have a cordial relationship between the two companies.


2. Compound Sentence
Contains 2 IC and connected by coordinating conjunction (FANBOYS).
First IC:
We are satisfied with all the details mention in the proposal
Coord. conjunction:
, and
Second IC:
we would like to offer the contract for one year.


3.  Complex Sentence
Contains 1 IC and 1 dependent clause (DC). DC begin with subordinating conjunction.
Subordinating conj. + One DC:
As + you have mentioned,
One IC:
we shall stick to the offer price specified in the proposal.


4. Compound-Complex Sentence
Contains 2 IC and 1 DC at least. connected by coordinating conj. & subordinating conj.
One DC:
We are pleased to inform you that in the meeting of the board of directors on 5th September,
First IC:
we have chosen your proposal to provide internet services to our company in the coming financial year
Coord. conjunction:
, and
Second IC:
we would like to know about the upcoming services next year.

Letter 2

Explanation

1.  Simple Sentences 
Contains 1 independent clause (IC).
One IC:
I have five years of experience working as a Marketing Strategist for one of our local retail clothing stores.


2. Compound Sentence
Contains 2 IC and connected by coordinating conjunction (FANBOYS).
First IC:
I recently read an article about United International’s new approach to digital marketing in Marketing Magazine Online
Coord. conjunction:
, and
Second IC:
I’m writing to inquire whether you have any marketing positions open.


3.  Complex Sentence
Contains 1 IC and 1 dependent clause (DC). DC begin with subordinating conjunction.
Subordinating conj. + One DC:
In addition of that,
One IC:
our sales increased by 50 percent during that time.


4. Compound-Complex Sentence
Contains 2 IC and 1 DC at least. connected by coordinating conj. & subordinating conj.
One DC:
that I got during the time I was in this role.
First IC:
My resume is enclosed with this letter
Coord. conjunction:
, so
Second IC:
you can review my education, work experience, and also my achievements 

Letter sources:
https://www.letters.org/business-letter/sample-business-letter.html
https://www.thebalancecareers.com/letter-of-interest-tips-and-samples-2059708
*letters are modified