Question 211231
Starting with the perimeter (P = 2(L+W)) which must be at least 120 meters ({{{P >=120)}}}, we have:
{{{2(L+W) >=120}}} but L = 2W "...rectangular garden...twice as long as it is wide...", so substitute L = 2W...
{{{2(2W+W) >=120}}} Simplify the left side and divide both sides by 2.
{{{3W >= 60}}} Divide both sides by 3.
{{{highlight(W >= 20)}}}
The width must be at least 20 meters.