Front

important

Back

crucial, essential, significant

Front

a lot of

Back

a large number of, several, countless

Front

very

Back

really,extremely, especially, particularly                     

Front

interesting

Back

fascinating, captivating, compelling

Front

problem

Back

an issue, a challenge, an obstacle, a hardship        

Front

big

Back

large, huge, massive, vast, colossal

Front

think

Back

consider, believe, suppose                                         

Front

good

Back

excellent, fine, positive, remarkable

Front

for example

Back

for instance, such as, in particular, as an example, namely