Answer
$(-\infty, 3)$
Work Step by Step
The idea is to isolate x on one side.
Adding, subtracting or multiplying/dividing with a positive number preserves order (the inequality symbol remains).
Multiplying/dividing with a negative number inverts the order (the inequality symbol changes)
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$ 5x+11\lt 26\qquad $ ... $/-11$
$ 5x\lt 15\qquad $ ... $/\div 3$, (positive)
$ x\lt 3$
The solution set is $(-\infty, 3)$ .
