To solve the equation \( 5x - 10x + 4 = 40 \), first simplify the left side:
Combine like terms:
\[ 5x - 10x = -5x \]
So the equation becomes:
\[ -5x + 4 = 40 \]
Next, isolate the \(x\) term by subtracting 4 from both sides:
\[ -5x = 40 - 4 \] \[ -5x = 36 \]
Now, divide both sides by -5:
\[ x = \frac{36}{-5} \] \[ x = -\frac{36}{5} \]
Thus, the solution is:
\[ x = -7.2 \]