Answer
$[6, \infty)$
Work Step by Step
"$ y $ is at least 4" $\qquad $ is written as $\quad y\geq 4.$
Substituing the expression for y,
$1-(x+3)+2x\geq 4 \qquad $ ... simplify
$1-x-3+2x\geq 4$
$ x-2\geq 4 \qquad $ ... add 2
$ x\geq 6$
Solution set = $[6, \infty)$.
