you treat the < as an equal sign, then test your results at the end

(x - 2)(x + 5) < 0

=> x - 2 < 0 or x + 5 < 0

=> x < 2 or x < -5

so now we basically think of, or draw a number line, placing the numbers -5 and 2 in there relative positions, and test what regions the original equation holds true for