Please use proper grouping symbols.
What you have is \(\displaystyle \frac{3x}{x}+2+\frac{2}{x}-1=\frac{5}{x^{2}}+x-2\)
I believe you mean:
\(\displaystyle \frac{3x}{x+2}+\frac{2}{x-1}=\frac{5}{x^{2}+x-2}\)
See?. Big difference without the proper grouping symbols. If the latter is correct, begin by factoring the quadratic and notice what it has in common with the other two denominators. Then, you'll have the LCD. As with any fraction, Make all denominators the same.