Question

va rog din suflet sa ma ajutati , rapid va rog , fara exercitiul 7 , rapid !

Answer 1

$1) \frac{x}{y} = \frac{2}{3}$

$3x = 2y$

$x = \frac{2y}{3}$

$\frac{6x + y}{x + 3y} = \frac{6 \times \frac{2y}{3} + y}{ \frac{2y}{3} + 3y } = \frac{ \frac{12y}{3} + y}{ \frac{2y}{3} + \frac{9y}{3} } = \frac{4y + y}{ \frac{2y + 9y}{3} }$

$= \frac{5y}{ \frac{11y}{3} } = 5y \times \frac{3}{11y} = \frac{5y \times 3}{11y} = \frac{15y}{11y} = \frac{15}{11}$

$2)A = {l}^{2}$

$A= 169$

${l}^{2} = 169$

$l = \sqrt{169}$

$l = 13$

$A = 196$

${l}^{2} = 196$

$l = \sqrt{196}$

$l = 14$

$P = 4l$

$P = 4 \times 13 = 52$

$P = 4 \times 14 = 56$

$3)a) \frac{15}{100} \times 2500 = 15 \times 25 = 375$

$b) \frac{0.4}{100} \times \frac{120}{17} = \frac{ \frac{4}{10} }{100} \times \frac{120}{17}$

$= \frac{4}{10} \times \frac{1}{100} \times \frac{120}{17} = \frac{4}{10} \times \frac{1}{10} \times \frac{12}{17}$

$= \frac{4 \times 1 \times 12}{10 \times 10 \times 17} = \frac{48}{1700} = \frac{24}{850} = \frac{12}{425}$

$4)b + f = 25$

$f = \frac{60}{100} \times 25 = \frac{60}{4} = 15$

$b + 15 = 25$

$b = 25 - 15$

$b = 10$

$\frac{x}{100}\times f=b$

$\frac{x}{100}\times 15=10$

$\frac{15x}{100}=10$

$15x=100\times10$

$15x=1000$

$x=\frac{1000}{15}$

$x=66.(6)$

$x=66.66$

$5) \frac{a}{b} = \frac{2}{3}$

$3a = 2b$

$a = \frac{2b}{3}$

$a - b = 15$

$\frac{2b}{3} - b = 15 \: | \times 3$

$2b - 3b = 45$

$- b = 45 \: | \times ( - 1)$

$b = - 45$

$a = \frac{2b}{3} = \frac{2 \times ( - 45)}{3} = - \frac{90}{3} = - 30$

$6) \frac{a}{0.1} = \frac{20}{b}$

$ab = 0.1 \times 20$

$ab = 2$

$17 + ab = 17 + 2 = 19$