Question

Solve the system of inequalities: |3-9a| less than or equal to 60

Answer 1

`|3-9a|\leq60\iff3-9a\leq60\ \wedge\ 3-9a\geq-60\qquad|-3\\\\-9a\leq57\ \wedge\ -9a\geq-63\qquad|\text{change the signs}\\\\9a\geq-57\ \wedge\ 9a\leq63\qquad|:9\\\\a\geq-(57)/(9)\ \wedge\ a\leq7\\\\a\geq-(19)/(3)\ \wedge\ a\leq7\to a\in\left[-(19)/(3),\ 7\right]`