from x15 to x 25 is 4 - -16 = -20 degree change
25 -15 = 10000 feet
-20/10 = -2 degrees every 1000 feet
$21.45 x 6 = $128.7
$128.7 + $10.60 = $139.3
Charlie will have saved $139.3 in 7 months
Given:
Triangle:
height = 6ft
base = 4ft
Rectangle:
length = x
Width = 6 ft
Surface Area = 150ft²
Area of a Triangle = h*b / 2 = (6ft * 4ft) / 2 = 12ft²
Area of a rectangle = Surface Area - Area of a Triangle
A = 150 ft² - 12 ft² = 138 ft²
138 ft² = x * 6ft
138 ft² / 6 ft = x
23 ft = x.