Why is it important to understand how to solve linear equations and inequalities ? also how can graphs be used to interpret solutions of the real-world problems ?

Understanding linear equations and inequalites is crucial because:
You must know this stuff to pass basic Algebra and math decently.
If you don't then you can't have a good job because most hardcore jobs require math.
If you don't know this basic math then people will laugh at you (trying to truthful for your own good)
so if I were you I'd be studying
But linear equations and inequalities are similar, just don't forget some basic rules on the signs.
Hope this helps!

45x is the correct answer