Two of them.
Four
3 of them.
Just the one and it is 4
There are four significant figures in 0.1050
Two
Two of them.
2 of them.
Two - the trailing zeros are not significant.
None of the zeros in that number are significant.
There are two significant figures in 85000
There are four significant digits in the number 1.071.
Three significant digits.
This number has seven significant digits.
All four of the digits given are significant digits.
There are two significant digits in the number 83.
All numbers which are not "zero" are classed as significant digits. Therefore in the number 129 there will be three digits which are classed as significant.