The value of the digit is 90
I think he is not correct because there is negative number so it can't be greater than one
*I am assuming that the hexagons in all questions are regular and the triangle in (24) is equilateral*
(21)
Area of a Regular Hexagon:
square units
(22)
Similar to (21)
Area =
square units
(23)
For this case, we will have to consider the relation between the side and inradius of the hexagon. Since, a hexagon is basically a combination of six equilateral triangles, the inradius of the hexagon is basically the altitude of one of the six equilateral triangles. The relation between altitude of an equilateral triangle and its side is given by:


Hence, area of the hexagon will be:
square units
(24)
Given is the inradius of an equilateral triangle.

Substituting the value of inradius and calculating the length of the side of the equilateral triangle:
Side = 16 units
Area of equilateral triangle =
square units
Unit rate means how much does it cost for 1 unit
140 for 18ft^2
divide by 18
140/18=7.77777777777777
so the unit rate is $7.78 per square foot
Give more information and I’ll help