Question

16 : (5-x) = 4 : 5 .Найдите х из пропорции.​

Answer 1

$\frac{16}{5-x} = \frac{4}{5}$

$5-x = 5 * 16/4 = 20$

x = -15

Answer 2

$16:(5-x)=4:5\\\\\\\dfrac{16}{5-x}=\dfrac{4}{5}\ \ \ \ \Rightarrow \ \ \ 16\cdot 5=4\cdot (5-x)\ \ ,\ \ \ 4\cdot 5=(5-x)\ \ ,\\\\\\20=5-x\ \ ,\ \ \ x=5-20\ \ ,\ \ \ \boxed{\ x=-15\ }$