1)
{2x+7 >1
{x - 3<1
{2x > 1 - 7
{x < 1 + 3
{x > (- 6)/2
{x < 4
{ x> - 3
{ x< 4
x∈ (-3;4)
2)
{3y<21
{4-y>0
{y < 21/3
{4 > y
{y<7
{y< 4
y∈(-∞,4 )
3)
{4х +9 > -15
{2-x<5
{4x> -15 -9
{2-5 < x
{4x > -24
{x >-3
{x>-24/4
{x>-3
{x>-6
{x>-3
x∈(-3; ∞ )
4)
{2x+3>x-1
{5x-22<x+2
{2x -x > -1-3
{5x-x< 2+22
{x>-4
{4x<24
{x>-4
{x<6
x∈(-4 , 6 )
5)
{7x+9<2x-1
{4+11x>9x-14
{7x-2x<-1-9
{11x-9x>-14-4
{5x<-10
{2x> - 18
{x<-2
{x> - 9
x∈ (-9, - 2)
6)
{x>0
{x-5>2x+1 ⇒ -5-1>2x-x
{x>0
{x< -6
х ∈ ∅ нет решении
у = - 9/34 + 13/51
у = - 27/102 + 26/102
y = - 1/102
2/3 - z = 0,4
2/3 - z = 4/10
2/3 - z = 2/5
z = 2/3 - 2/5
z = 10/15 - 6/15
z = 4/15
4/7 + t = 7/10
t = 7/10 - 4/7
t = 49/70 - 40/70
t = 9/70