To solve the equation \( 2x + 5x - 8 = 20 \), we first combine like terms on the left side of the equation:
\[ 2x + 5x = 7x \]
So, we can rewrite the equation as:
\[ 7x - 8 = 20 \]
Next, we isolate \( 7x \) by adding \( 8 \) to both sides:
\[ 7x - 8 + 8 = 20 + 8 \]
This simplifies to:
\[ 7x = 28 \]
Now, we solve for \( x \) by dividing both sides by \( 7 \):
\[ x = \frac{28}{7} = 4 \]
Checking the Solution
We can substitute \( x = 4 \) back into the original equation to verify:
\[ 2(4) + 5(4) - 8 = 20 \]
Calculating:
\[ 8 + 20 - 8 = 20 \] \[ 20 = 20 \]
Since both sides of the equation are equal, our solution is correct.
Thus, the solution to the equation is:
\[ \boxed{4} \]