Find the inequality of X≥3 or x ≤- 1/2.
According to x≥a is 2x &;; # 178; A necessary and sufficient condition for -5x-3≥0
That is, x≥a can be deduced as X≥3 or x ≤- 1/2.
Therefore, a≥3
If you can read the number axis and understand the range of values, then there is no problem!