f- numărul fetelor
b- numărul băietu
f+b=150
[tex] \frac{b - 10}{2} = \frac{f}{3} \times 2[/tex]
[tex] \frac{b - 10}{2} = \frac{2f}{3} [/tex]
[tex]3(b - 10) = 2 \times 2 \times f[/tex]
[tex]3b - 30 = 4f[/tex]
[tex]f = \frac{3b - 30}{4} [/tex]
[tex] \frac{3b - 30}{4} + b = 150[/tex]
[tex] \frac{3b - 30}{4} + \frac{4b}{4} = 150[/tex]
[tex]\frac{3b - 30 + 4b}{4} = 150[/tex]
[tex]\frac{7b - 30}{4} = 150[/tex]
[tex]7b - 30 = 4 \times 150[/tex]
[tex]7b - 30 =600[/tex]
[tex]7b = 600 + 30[/tex]
[tex]7b = 630[/tex]
[tex]b = 630 \div 7 = 90[/tex]
[tex]f = 150 - 90 = 60[/tex]
