A shelf is supported with brackets as pictured in the diagram below. What is the width of the shelf?
A 14 in.
B 16 in.
C 12 in.
D 10 in.

or

step-by-step explanation:

we need to solve for 'x' the following equation:  

we have that:

⇒

⇒ ⇒

factorizing, we get that:

  ⇒

then, the solutions are: or

nothing extraneous has been found!

the answer is b.6

step-by-step explanation:

so mark-up is 0.4 multiplied by 180 = 72