Hi there!
Let's solve this equation step by step!
First work out the parenthesis on the left side. This can for instance be done using rainbow technique.
Collect the terms on the left
(add 4x to -x).
Now we can see that we have two identical expressions. Therefore, it doesn't matter what value of x you plug into the equation, the equation will always be true. Hence, the answer is D. [the equation has] infinitely many [solutions].
~ Hope this helps you!