\(1500:\left[\left(30x+40\right):x\right]=30\)
\(\left[\left(30x+40\right):x\right]=1500:30\)
\(\left[\left(30x+40\right):x\right]=50\)
\(30x:x+40:x=50\)
\(30+40:x=50\Leftrightarrow40:x=50-30\)
\(40:x=20\Leftrightarrow x=40:20\Leftrightarrow x=2\)
1500 : [(30.x+40):x] = 30
\(\left(30.x+40\right):x=50\)
=> 30.x + 40 = 50.x
=> 30.x - 50.x = -40
-20x = -40
x = 2