Answer:
x = 6 cm
Explanation:
The equilateral triangular prism below has 2 triangle and 3 rectangle .To calculate the surface area we have to sum the area of each simple shape.
The triangle is an equilateral triangle , that means the sides are all equal.
Area of triangle = 1/2 bh
where
b = base = x cm
h = height = 6 cm
area = 1/2 × x × 6
area = 6x/2
area = 3x
For two triangle = 3x + 3x = 6x
Area of the rectangle = Lb
where
L = 12 cm
b = x cm
area = 12x
For 3 rectangles = 12x + 12x + 12x = 36x
Therefore,
6x + 36x = 252
42x = 252
divide both sides by 42
x = 252/42
x = 6 cm