It depends on how you count them. If you describe them by their dimensions, lowest one first, you can have
1 x 1 x 18
1 x 2 x 9
1 x 3 x 6
2 x 3 x 3
Of course, these dimensions can be put in any order.
-25 - 12x = -(-8x - 6) - 3(5x + 12)
Distributive property.
-25 - 12x = 8x + 6 - 15x - 36
Combine like terms.
-25 - 12x = -7x - 30
Add 12x to both sides.
-25 = 5x - 30
Add 30 to both sides.
5 = 5x
Divide both sides by 5.
x = 1
The x-intersect is 1.
