Step-by-step explanation:

3x + 4 = 2x + 8

To isolate the variable (x) on one side, we can subtract 2x from both sides:

3x + 4 - 2x = 2x + 8 - 2x

Simplifying:

x + 4 = 8

Subtracting 4 from both sides:

x + 4 - 4 = 8 - 4

Simplifying:

x = 4

Therefore, the solution is x = 4.

5x + 5 = 2x - 4

To isolate the variable (x) on one side, we can subtract 2x and 5 from both sides:

5x + 5 - 2x - 5 = 2x - 4 - 2x - 5

Simplifying:

3x = -9

Dividing both sides by 3:

3x/3 = -9/3

Simplifying:

x = -3

Therefore, the solution is x = -3.

7y + 3 = 3y + 31

To isolate the variable (y) on one side, we can subtract 3y from both sides:

7y + 3 - 3y = 3y + 31 - 3y

Simplifying:

4y + 3 = 31

Subtracting 3 from both sides:

4y + 3 - 3 = 31 - 3

Simplifying:

4y = 28

Dividing both sides by 4:

4y/4 = 28/4

Simplifying:

y = 7

Therefore, the solution is y = 7.