Answer: the length is 15 m and the width is 5 m
Explanation:
Let L represent the original length of the rectangle.
Let W represent the original width of the rectangle.
The length of a rectangle is three times it's width. This means that
L = 3W
If the width is diminished by 1 m and length is increased by 3 m, the area of the rectangle that is formed is 72 m². This means that
(L + 3)(W - 1) = 72
LW - L + 3W - 3 - 72 = 72 + 3
LW - L + 3W = 75 - - - - -- - - - - - 1
Substituting L = 3W into equation 1, it becomes
3W × W - 3W + 3W = 75
3W² = 75
W² = 75/3 = 25
W = √25 = ±5
The width cannot be negative. Therefore, the width is 5 m
L = 3W = 3 × 5 = 15 m