Rose, net is gross minus debt.
Her house is valued at $200,000 but has a mortgage for $150,000. She's up $50,000 because what she has is worth more than she owes.
Same with the car. She's up $12,000.
Her credit card balance is a debt, so that's $-800.
If she has $1200 in the bank, then that's another $1200 in her favor.
$50,000 + $12,000 + $1200 - $800 = $62,400 in net worth.
Hope this helps!