1.Aflați x€N din proporția:
a)2x supra 3=7 supra 4
b)4 supra 5x=11 supra 20
c)7 supra 2=3x supra 17

2.Aflati 30% din 20% din 25% din 400.

1). a) 2x / 3 = 7 / 4 ⇒ 2x·4 = 3·7 ⇒ x = 21 / 8 = 2,625 ;

b) 4 / 5x = 11 / 20 ⇒ 11·5x = 20·4⇒ x = 80 / 55 = 16 / 11 = 1,(45) ;

c) 7 / 2 = 3x / 17 ⇒ 3x·2 = 17·7 ⇒ x = 119 / 6 = 19,8(3) ;

2). [tex] \frac{30}{100}\cdot\frac{20}{100}\cdot\frac{25}{100}\cdot400=6 [/tex]

[tex] 1.a)\frac{2x}{3}=\frac{7}{4}\\ \\2x \cdot4=3 \cdot7\\ \\ x=\frac{21}{8} \\ \\\\ b)\frac{4}{5x}=\frac{11}{20}\\ \\11 \cdot 5x=20 \cdot4\\ \\ x=\frac{80}{55}=\frac{16}{11} \\ \\\\ c)\frac{7}{2}=\frac{3x}{17}\\ \\3x \cdot2=17 \cdot7\\ \\ x=\frac{119}{6} [/tex]

[tex]2. \frac{30}{100}\cdot\frac{20}{100}\cdot\frac{25}{100}\cdot400=6 [/tex]