To solve this equation, we first need to distribute the 5 on both terms inside the parentheses:

5(7 + 3x) - 5(7 + 7x) = 0
35 + 15x - 35 - 35x = 0

Next, combine the like terms:

15x - 35x = -20x

Now the equation becomes:

35 - 35 - 20x = 0
-20x = 0

To solve for x, divide both sides by -20:

x = 0

Therefore, the solution to the equation is x = 0.