Given that, one side of the garden be 10 feet long.
So, length : l = 10 feet.
And the other side will be 5 less than three times the first side.
So, width = 3l - 5
= 3(10) - 5 Since l: length = 10
= 30 - 5
= 25
So, area = Length * width
= 10 * 25
= 250.
So, the area of Mark's garden is 250 square feet.
Hope this helps you!