Percent problems

Mr. Nowak obtained the income of $20200$ zlotys from his business activity in $2011$. He settled with the tax office, paying a tax in the amount of $19\mathrm{\%}$ of his income. In $2011$, Mr. Nowak's income tax amounted to:

$1100$ people were asked to say which of the following activities (cooking, ironing, playing a musical instrument) they are bad at. $42\mathrm{\%}$ of them are bad at cooking, $67\mathrm{\%}$ of them are bad at ironing, $85\mathrm{\%}$ of them are bad at playing a musical instrument. How many people who can cook can we expect in the group of $1200$ people?

A phone subscription in Telekomunikacja Polska is $35$ zlotys. How much is the subscription fee if you add up a $7\mathrm{\%}$ tax to it?

How much pure gold contains a ring weighing $7$ grams if the gold fineness is $750$? (That means, the gold content is $75$ percent.)