Question

4 - 2x = x + 31


5 - 2(y - 1) = y + 4(-2 + 3y)


7a - (2a - 1) = 4 + (a - 6)

Answer 1

Incógnitas de um lado, números do outro. Lembrando que, ao mudar de lado, a operação muda.

$4 - 2x = x + 31 \\\\ -2x - x = 31-4 \\\\ -3x = 27 \\\\ -x = \frac{27}{3} \\\\ -x = 9 \ \ \times (-1) \\\\ \boxed{\boxed{x = -9}}$


$5 - 2 \cdot (y - 1) = y + 4 \cdot (-2 + 3y) \\\\ 5-2y+2 = y -8 + 12y \\\\ -2y - y - 12y = -8 - 5 - 2 \\\\ -15y = -15 \\\\ y = \frac{-15}{-15} \\\\ \boxed{\boxed{y = 1}}$


$7a - (2a - 1) = 4 + (a - 6) \\\\ 7a - 2a + 1 = 4 + a - 6 \\\\ 7a-2a-a = 4-6-1 \\\\ 4a = -3 \\\\ \boxed{\boxed{a = -\frac{3}{4}}}$

Answer 2

a)
4 - 2x = x + 31
-2x - x = 31 - 4
-3x = 27
x= -9

b)
5 - 2(y - 1) = y + 4(-2 + 3y)
5 -2y + 2 = y - 8 +12y
-2y - y -12y = -8 - 5 - 2
-15y = -15
y = 1

c)
7a - (2a - 1) = 4 + (a - 6)
7a - 2a +1 = 4 + a - 6
7a - 2a - a = 4 - 6 - 1
4a = -3
a=-3/4