Answer
$(7,\infty)$
Work Step by Step
$20+x\lt6x-15$
Solve for x by subtracting x from each side, adding 15 to each side, then dividing each side by 5.
$20+x-x\lt6x-15-x$
$20\lt5x-15$
$20+15\lt5x-15+15$
$35\lt5x$
$35\div5\lt5x\div5$
$7\lt x$
$x\gt7$
This is expressed in interval notation as
$(7,\infty)$
where ( indicates that the solution set for x approaches but does not include 7.