Assets - equity = liabilities
So liability before the increase is:
300, 000 - 100, 000 = 200, 000
And if assets increases by 80, 000. Hence new assets = 380, 000. Liabilities increases by 50, 000; hence new liability = 250, 000.
New Equity = New Assets - New liability.
New Equity = 380, 000 - 250, 000 = 130, 000.