Răspuns :

Bună,:)

[tex]a) \frac{3}{7} = \frac{x}{28} = > x = \frac{28.3}{7} = 4.3 = 12[/tex]

[tex]b) \frac{3}{7} = \frac{45}{x} = > x = \frac{7.45}{3} = 7.15 = 105[/tex]

[tex]c) \frac{3}{7} = \frac{(2x + 1)}{21} \: \: \: \: \: \: \: 7(x + 1) = 21.3 \: \: \: \: 14x + 7 = 63 \: \: \: \: \: 14x = 56 \: = > 56 \div 14 = 4[/tex]

[tex]d) \frac{51}{(38 + x)} = \frac{3}{7} = > 51 \times 7 = (38 + x) \times 3 + | \div 3[/tex]

[tex]17 \times 7 = 38 + x[/tex]

[tex]119 = 38 + x | - 38 = > x = 81[/tex]

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