<span>55:5-5-5=1; </span>
<span>(5-5)*5*5*5=0; </span>
<span>(5+5+5-5):5=2; </span>
<span>(5-5:5-5:5)=3; </span>
<span>(5+5+5+5):5=4: </span>
<span>5*5-5*5+5=5; </span>
<span>(5+5):(5+5)+5=6; </span>
<span>5:5+5:5 +5=7; </span>
<span>(5+5+5):5+5=8; </span>
<span>(55-5-5):5=9: </span>
<span>55:5-5:5=10</span>
56 ≤ 7а ≤ 63. 6 ≤ 3b ≤ 9
-9 ≤ -3b ≤ -6
Ответ : 45 ≤ 7a - 3b ≤ 57
1) х+7=0
х=-7
3) х-7=0
х=7
4) 5-2х=0
-2х=-5
х=2,5
5) 4х+1=11
4х=11-1
4х=10
х=2,5
6)2-5х=0
-5х=-2
х=0,4