1) 9-3=6 6*8=48 стульев
2) 8+2=10 10*9=90 стульев.
3) 9+1=10 10*8=80 стульев.
Фото кидать нельзя а так fotomath скачай там поможет
1)
/////////////////////////////////////////////
--------(1)-------------------(2,5)--------------
\\\\\\\\\\\\\\\\\\\\\\\\\\
x∈(2,5;∞)
2){x≥1,5
{x≤3
//////////////////////////////////////////////////////
---------[1,5]----------------------[3]---------------
\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\
x∈[1,5;3]
3
/////////////////////////////////////////////////////
------------(-2)---------------------(-1,5)----------------
\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\
x∈(-2;-1,5)
4
{5x<5⇒x<1
{x<12
\\\\\\\\\\\\\\
---------(1)---------------------(12)-----------
///////////////////////////////////////////
x∈(-∞;1)
5
{x≤15
{x≥6
\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\
--------[6]------------------[15]-----------
/////////////////////////////////////////
x∈[6;15]
6
{x>0
{x≥-7
/////////////////////////////////////////////
----------[-7]--------------------(0)----------------
\\\\\\\\\\\\\\\\\\
x∈(0;∞)
1)8*4=32( листа понадобилось на 8 папок)
2)50-32=18 ( листов осталось)