At the end of the fiscal year, an adjusting entry is made that increases salaries payable and salaries expense. this entry is an application of which accounting principle?

The accounting principle that was made is called matching. At the end of the fiscal year, the usual adjusting entry for depreciation on equipment was omitted, total assets will be understated at the end of the current year.  Income Summary will be close to retained earnings at the end of fiscal year accounts will be closed to the retained earnings account. 

month 1 start amount =$3287.90 interest=(3287.90x0.0145/12)3.97 total to pay=$3291.81 paid =$1200 balance =$2,091.87

month 2 starting amount= $2,091.87 interest =$25.28 total to pay =$2117.15 paid =$1200 balance $917.15

month 3 starting amount =$917.15 interest =$11.08 total to pay =$928.23 paid =$928.23 balance =$0 total to pay 1200+1200+928.23 = $3328.23 it will take 3 months to pay a total of $3328.23

i would say a penny hope it you