Question

400-(18+705:x)*4=140

Answer 1

$400-(18+705:x)*4=140$
$(18+705:x)*4=400-140$
$(18+705:x)*4=260$
$18+705:x=260:4$
$18+705:x=65$
$705:x=65-18$
$705:x=47$
$x=705:47$
$x=15$
Ответ: $15$

Answer 2

400-(18+705:x)*4=140
400-72-2820:x=140
2820:x=188
x=2820:188
x=15