Question

найдите значение х из пропорции 2/Х+2=7/28 2х/3=4/9 Х-3/30=3/10

Answer 1

2 / ( X + 2 ) = 7 / 28 
28 * 2 = 7 * ( X + 2 ) 
56 = 7X + 14 
7X = - 42 
X = - 6 
-------------------------
2X / 3 = 4 / 9 
2X * 9 = 4 * 3 
18X = 12 
X = 12/18 
X = 2/3 
--------------------------
( X - 3 ) / 30 = 3 / 10 
10 * ( X - 3 ) = 3 * 30 
10X - 30 = 90 
10X = 120 
X = 12