simple _adjective 

NOUNS 

question • answer, explanation
・We raised a simple question during the meeting.

solution, plan, design
・They have a simple solution.

approach, way, method, technique
・We prefer a simple approach.

process 
・Ordering groceries online has become a simple process.

idea • task, test
・I presented a simple idea to the team.

rules • instructions
・She gave her kids some simple rules to follow at the park.

life
・He leads a simple life.

ADVERBS

very, perfectly, so, extremely, incredibly, remarkably
・The answer to the question is extremely simple.

relatively, quite, fairly, pretty, rather, comparatively
・Last semester's exams were relatively simple.

enough
・That's simple enough.

beautifully, delightfully, elegantly, wonderfully
・The interface of the website is beautifully simple.

deceptively, apparently, seemingly, surprisingly
・The puzzle may seem deceptively simple at first.

VERBS

seem, be, appear • become 
・The task initially seemed simpler than expected.

look, sound, remain
・The recipe sounds simple; I think I'll give it a try.

keep, make 
・Keep your approach to the problem as simple as you can.

prove • find
・He found the math problem quite simple.

PHRASES

simple to use/make/operate etc.
The coffee machine is very simple to operate – just press a button.

simple but effective
Boost your productivity using this simple but effective technique.

in simple terms
To put it in simple terms, gravity is what keeps us on the ground.

it’s as simple as that
Saving money involves spending less than you earn. It's as simple as that.

clear and simple 
The advertisement conveys a clear and simple message.

simple and straightforward
She gave a simple and straightforward answer to the question.