ANSWER

EXPLANATION
We want to find the constant that must be added to

to form a perfect square.
Comparing the given expression to

we have
a=1 , b=-3 , and c=0.
We need to add

We substitute the values to get,

We change this to mix numbers to get,

The last choice is correct.
Given that the perimeter of rhombus ABCD is 20 cm, the length of the sides will be:
length=20/4=5 cm
the ratio of the diagonals is 4:3, hence suppose the common factor on the diagonals is x such that:
AC=4x and BD=3x
using Pythagorean theorem, the length of one side of the rhombus will be:
c^2=a^2+b^2
substituting our values we get:
5²=(2x)²+(1.5x)²
25=4x²+2.25x²
25=6.25x²
x²=4
x=2
hence the length of the diagonals will be:
AC=4x=4×2=8 cm
BD=3x=3×2=6 cm
Hence the area of the rhombus wll be:
Area=1/2(AC×BD)
=1/2×8×6
=24 cm²
Bob is the fourth child, as the sentence states "Bobs FATHER"