Answer:
a. $583,000
b.  $878,000
c. $330,000
Explanation:
In this question, we have to use the accounting equation which is presented below:
Total assets = Total liabilities + stockholder's equity
$864,000 = $523,000 + stockholder's equity
So, the stockholder's equity = $864,000 - $523,000 = $341,000
a. New assets = Old assets + addition 
                        = $864,000 + $156,000
                        = $1,020,000
New liabilities =  Old liabilities - reduction 
                        = $523,000 - $86,000
                        = $437,000
So, the stockholder's equity = $1,020,000 -  $437,000 = $583,000
b. New liabilities =  Old liabilities + addition 
                            = $523,000 + $91,000
                            = $614,000
New equity =  Old equity - reduction 
                    =  $341,000 - $77,000 
                    = $264,000
So, the total assets = New liabilities + New equity  
                                 =  $614,000 + $264,000
                                 = $878,000
c. New assets = Old assets - reduction 
                        = $864,000 - $90,000
                        = $774,000
New equity = Old equity + addition
                    = $341,000 + $103,000
                    = $444,000
So, the total liabilities = $774,000 - $444,000 = $330,000