Well let me help.
For the first Question, the question is asking for the perimeter of the plot so assuming the plot is a rectangle, the perimeter will be (2*3)+(2*4.3)
=6+8.6
=14.6km.
Question 2
The problem involves finding the perimeter of the triangular garden. since the garden is an equilateral triangle, the perimeter will be thrice the side given ("equilateral" means "equal sided triangle"). So the answer will be 3*4.5
= 13.5 km.
Question 3
Same type of question as Q2 but this type is isosceles triangle (only two equal sides with one being different)
So the perimeter will be (2*15)+20
=30+20
=50km.
I hope this'll help