Question

frac{y}{13}=frac{25}{52}

Answer 1

Решаем пропорцией: 
$52y = 13*25$ 
$y = frac{13*25}{52}$ 

$y = 6,25$

Answer 2

$frac{y}{13}=frac{25}{52};\\13*25=52y;\\13*25=13*4y;\\y=frac{25}{4};\\y=6.25;$

 

ответ: 6.25