A) 10% de x = 27

[tex] \frac{10}{100} .x = 27[/tex]

[tex] \frac{10x}{100} = 27[/tex]

[tex]10x = 27 \: . \: 100[/tex]

[tex]10x = 2700[/tex]

[tex]x = 2700 \div 10[/tex]

[tex]x = 270[/tex]

B) 1% de x = 15

[tex] \frac{1}{100} .x = 15[/tex]

[tex] \frac{x}{100} = 15[/tex]

[tex]x = 15 \: . \: 100[/tex]

[tex]x = 1500[/tex]

C) 25% de x = 100

[tex] \frac{25}{100} .x = 100[/tex]

[tex] \frac{25x}{100} = 100[/tex]

[tex]25x = 100 \: . \: 100[/tex]

[tex]25x = 10000[/tex]

[tex]x = 10000 \div 25[/tex]

[tex]x = 400[/tex]