How do I find the missing amounts from balance sheet and income statement data

How do I find the missing amounts from balance sheet and income statement data. Determine the missing amounts, but first determine amount of increase or decrease in owners equity during the year.

Beg:
Assets:$300,000
Liabilties:$120,000
End:
Assets:$420,000
Loabilities:$110,000
During the year
Add investment (a)
Withdrawls:25,000
Revenues:$190,000
Expenses$80,000
How do I find the missing amount in the letter (a)