Gonna fix some typos with your question:
Carl wants to plant a garden that is 1 1/2 yards long with an area of 3 1/2 square yards. What is the width of the garden?
So with these type of questions, we divide 3 1/2 by 1 1/2, to find the missing length:
3 1/2 ÷ 1 1/2 = 2 1/3.
The width of Carl's garden is 2 1/3 square yards.