Suma pary liczb przeciwnych jest równa 0.

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a)

Najpierw daną liczbę będziemy "uzupełniać" do $0,$ a następnie będziemy dodawać liczbę, jaką brakuje nam do wyniku.

$-16+\dots \dots .=32$     

$-16+\underset{48}{\underbrace{16+32}}=0+32=32$   
Zatem: 

$-16+\underline{48}=32$   

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$16+\dots \dots =-16$      

$16+\underset{-32}{\underbrace{\left(-16\right)+\left(-16\right)}}=0+\left(-16\right)=-16$  
Zatem:

$16+\underline{\left(-32\right)}=-16$       

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$16+\dots \dots =-32$      

$16+\underset{-48}{\underbrace{\left(-16\right)+\left(-32\right)}}=0+\left(-32\right)=-32$    
Zatem:

$16+\underline{\left(-48\right)}=-32$     

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b)

$-25+\dots \dots =-10$  

$-25+15=-\left(25-15\right)=-10$  

Zatem:

$-25+\underline{15}=-10$     

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$-25+\dots \dots =10$  

$-25+\underset{35}{\underbrace{25+10}}=0+10=10$  
Zatem:

$-25+\underline{35}=10$  

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$25+\dots \dots =-25$  

$25+\underset{-50}{\underbrace{\left(-25\right)+\left(-25\right)}}=0+\left(-25\right)=-25$
Zatem:

$25+\underline{\left(-50\right)}=-25$  

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c)

$-\frac{1}{4}+\dots \dots =0$  

$-\frac{1}{4}+\frac{1}{4}=\frac{1}{4}-\frac{1}{4}=0$     

Zatem: 

$-\frac{1}{4}+\underline{\frac{1}{4}}=0$  

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$\frac{1}{4}+\dots \dots =-1$    

$\frac{1}{4}+\underset{-1\frac{1}{4}}{\underbrace{\left(-\frac{1}{4}\right)+\left(-1\right)}}=0+\left(-1\right)=-1$    
Zatem: 

$\frac{1}{4}+\underline{\left(-1\frac{1}{4}\right)}=-1$   

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$-\frac{1}{4}+\dots \dots =\frac{1}{4}$    

$-\frac{1}{4}+\underset{\frac{2}{4}=\frac{1}{2}}{\underbrace{\frac{1}{4}+\frac{1}{4}}}=0+\frac{1}{4}=\frac{1}{4}$  
Zatem:

$-\frac{1}{4}+\underline{\frac{1}{2}}=\frac{1}{4}$