7)
[tex]t+f=55\\\displaystyle \frac{t}{f}=\frac83\Rightarrow 3t=8f\Rightarrow t=\frac{8f}{3}\\\displaystyle\frac{8f}{3}+f=55\\\\\displaystyle\frac{8f+3f}{3}=55\\\\11f=55\cdot3=165\\f=15\text{ ani}\\f=55-f=40\text{ ani}[/tex]
8)
[tex]a+b+c=360\\a=3c\\\\\displaystyle\frac{a}{b}=\frac34\Rightarrow4a=3b\Rightarrow b=\frac{4a}{3}=\frac{12c}{3}=4c\\3c+4c+c=360\\8c=360\\c=45\text{ lei}\\a=3c=135\text{ lei}\\b=4c=180\text{ lei}[/tex]
