При каком значении а уравнение (2+а)x=10

При таком значение уравнение будет правильным a=3.x=2

Решение
1)  (x+3)(x-4)=-12
x² - x - 12 = - 12
x(x - 1) = 0
x₁ = 0
x₂ = 1
ответ: х₁ = 0 : х₂ = 1

2)  (3x-1)^2=1
3x - 1 = - 1
3x = 0
 x₁ = 0

3x - 1 = 1
 3x = 2
x₂ =  2/3 
ответ: х₁ = 0; х₂ = 2/3

3)  (2x+3)(3x+1)=11x+30
6x² + 11x + 3 = 11x + 30
6x² = 27
x² = 9/2
x₁ = - 3√2/2
x₂ = 3√2/2
ответ: x₁ = - 3√2/2; x₂ = 3√2/2

4)  18-(x-5)(x-4)=-2
x² - 9x + 20 = 20
x(x - 9) = 0
x₁ = 0
x₂ = 9
ответ: x₁ = 0 ; x₂ = 9

5)  5x+(2x+1)(x-3)=0
5x + 2x² - 5x - 3 = 0
2x² - 3 = 0
2x² = 3
x² = 3/2
x₁ = - √6/3
x₂ = √6/3

6)  x^2-5=(x-5)(2x-1)
x² - 5 = 2x² - 11x + 5
x² - 11x + 10 = 0
x₁ = 1
x₂ = 10
ответ: x₁ = 1 ; x₂ = 10

А) 3х-8=х+6 
3*x-8 = x+6
3*x = 14 + x
2*x = 14
x = 14 / (2)

б) 7а-10=2-4а
7*a-10 = 2-4*a
7*a = 12 - 4*a
11*a = 12
a = 12 / (11)

в) 1/6y-1/2=3-1/2y
1/6*y-1/2 = 3-1/2*y
y/6 = 7/2 - y/2
2*y/3 = 7/2
y = 7/2 / (2/3)
y = 21/4


г) 2.6-0.2b=4.1-0.5b
(13/5)-(1/5)*b = (41/10)-(1/2)*b
13/5-1/5b = (41/10)-(1/2)*b
13/5-1/5b = 41/10-1/2b
-b/5 = 3/2 - b/2
3*b/10 = 3/2
3/10b = 3/2 / (3/10)
b = 5

д) p-1/4=3/8+1/2p
p-1/4 = 3/8+1/2*p
p = 5/8 + p/2
p/2 = 5/8
/2p = 5/8 / (1/2)
p = 5/4

е) 0.8-y=3.2+y
4/5)-y = (16/5)+y
4/5-y = (16/5)+y
4/5-y = 16/5+y
-y = 12/5 + y
-2*y = 12/5
-2y = 12/5 / (-2)
y = -6/5

ж) 2/7х=1/2
2/7*x = 1/2
x = 1/2 / (2/7)
x = 7/4

з) 2х-0,7=0
2*x-(7/10) = 0
2*x-7/10 = 0
2*x = 7/10
2x = 7/10 / (2)
 x = 7/20