Answer:
December 31 
Dr Supplies expense $2100 
Cr Supplies $2100
December 31
Dr Insurance expense $1,550 
Cr Prepaid insurance $1,550
December 31 
Dr Salaries expense $15,100 
Cr Salaries payable $15,100
December 31
Dr Deferred revenue $1,050 
Cr Rent revenue $1,050
Step-by-step explanation:
Preparation of the adjusting entries that were made for supplies, prepaid insurance, salaries payable, and deferred revenue on December 31.
December 31 
Dr Supplies expense $2100 
Cr Supplies $2100
( $1,550+3,600-$3,050= $2100)
( To record supplies expense) 
December 31
Dr Insurance expense $1,550 
Cr Prepaid insurance $1,550
( To record insurance expense) 
December 31 
Dr Salaries expense $15,100 
Cr Salaries payable $15,100
( To record salaries expense) 
December 31
Dr Deferred revenue $1,050 
Cr Rent revenue $1,050
($3,150 x 1/3= $1,050)
( To record rent revenue)