Answer:
Firstly, rewrite the equation:
⅓ (18 + 27) = 81
Substitute x for the given number of it's supposed equivalent.
In this case x = 12.
⅓ (18(12) + 27) = 81
Solve using PEMDAS and simplify what is in the parenthesis first. Then, multiply.
(18 x 12) + 27 = 243
Now, solving using PEMDAS, multiply the total of what you got that was originally in the parenthesis by ⅓ .
⅓ (243) = 81
When you multiple these number they are equivalent to 81.
81 = 81
Since the equation given, when substituted x for 12, is equivalent to 81, this proves that substituting x for 12 makes this equation true.