Is it possible to calculate a percentage from a cell that contains two numbers and text within the same cell? And is this possible without separating the numbers into separate cells?

E.g. If A1 contained the value "4 (19)", is it possible to create a formula to use the cell contents to calculate a percentage of 21% i.e. 4 of 19?

Similarly, if B1 contained the value "10 (20)", to calculate this as 50% (formula result in B2)?

The second number will always be in brackets.

Many thanks,