To solve this equation, we first need to simplify the left side of the equation by combining the terms within the parentheses:

(0.7x - 0.2x) 6.4
= 0.5x 6.4
= 3.2x

Now we have the simplified expression:

3.2x = 9.6

Next, we need to solve for x by dividing both sides by 3.2:

3.2x / 3.2 = 9.6 / 3.2
x = 3

Therefore, the value of x is 3.