$\text{a)}28+75\%\cdot 28=28+\frac{3}{{\sout{4}}^1}\cdot {\sout{28}}^7=28+21=49$

$\text{lub}175\%\cdot 28=\frac{{\sout{175}}^7}{{\sout{100}}^4}\cdot 28=\frac{7}{{\sout{4}}^1}\cdot {\sout{28}}^7=49$  

$\text{b)}4+0,5\%\cdot 4=4+0,005\cdot 4=4+0,02=4,02$

$\text{lub}100,5\%\cdot 4=\frac{100,5}{{\sout{100}}^{25}}\cdot {\sout{4}}^1=\frac{100,5}{25}=4\frac{0,5}{25}=4\frac{2}{100}=4,02$   

 

$\text{c)}52+110\%\cdot 52=52+1,1\cdot 52=52+57,2=109,2$  

$\text{lub}210\%\cdot 52=\frac{{\sout{210}}^{21}}{{\sout{100}}^{10}}\cdot 52=2,1\cdot 52=109,2$  

 

$\text{d)}45-24\%\cdot 45=45-\frac{24}{100}\cdot 45=45-\frac{6}{{\sout{25}}^5}\cdot {\sout{45}}^9=45-\frac{54}{5}=45-10\frac{4}{5}=34\frac{1}{5}=34,2$  

$\text{lub}76\%\cdot 45=\frac{76}{{\sout{100}}^{20}}\cdot {\sout{45}}^9=\frac{684}{20}=34,2$  

 

$\text{e)}250-0,1\%\cdot 250=250-0,001\cdot 250=250-0,25=249,75$  

$\text{lub}99,9\%\cdot 250=\frac{99,9}{{\sout{100}}^2}\cdot {\sout{250}}^5=\frac{499,5}{2}=249,75$  

 

$\text{f)}32-2,5\%\cdot 32=32-\frac{{\sout{2,5}}^1}{{\sout{100}}^{40}}\cdot 32=32-\frac{1}{{\sout{40}}^5}\cdot {\sout{32}}^4=32-\frac{4}{5}=32-\frac{8}{10}=32-0,8=31,2$  

$\text{lub}97,5\%\cdot 32=\frac{97,5}{{\sout{100}}^{25}}\cdot {\sout{32}}^8=\frac{780}{25}=31,2$