7.
[tex] \frac{x}{y} = \frac{3}{8} = > x = \frac{3y}{8} [/tex]
[tex]x + y = 44 = > \frac{3y}{8} + y = 44 = > \\ \frac{3y}{8} + \frac{8y}{8} = 44 = > \frac{11y}{8} = 44 = > \\ 11y = 44 \times 8 = > 11y = 352 = > \\ y = 352 \div 11 = > \\ y = 32[/tex]
8.
[tex] \frac{x}{y} = \frac{5}{7} = > x = \frac{5y}{7} [/tex]
[tex]x - y = 36 = > \frac{5y}{7} - y = 36 = > \\ \frac{5y}{7} - \frac{7y}{7} = 36 = > - \frac{2y}{7} = 36 = > \\ - 2y = 36 \times 7 = > - 2y = 142 = > \\ y = - 71 \\ \\ x = \frac{5y}{7} = \frac{5 \times ( - 71)}{7} = - \frac{355}{7} [/tex]
9.
[tex] \frac{2x + 3y}{10} = \frac{3x + 1}{14} = > \\ 14 \times (2x + 3y) = 10 \times (3x + 1) = > \\ 28x + 42y = 30x + 10 = > \\ 42y = 2x + 10 = > 21y = x + 10 = > \\ x = 21y - 5[/tex]
[tex]x + y = 35 = > 21y - 5 + y = 35 = > \\ 22y - 5 = 35 = > 22y = 40 = > \\ y = \frac{40}{22} = > y = \frac{20}{11} [/tex]
14. a)6x=5y=>x/y=5/6
b)nu se înțelege,spune mi enuntul si ti l fac
15. a/b=2/3
2a+b=28
a/b=2/3=>b=3a/2
2a+b=28
2a+3a/2=28
4a/2+3a/2=28
7a/2=28
7a=56
a=8
b=3a/2
b=(3×8)/2
b=24/2
b=12
