Question

What's the answer for 12=0.9a

Answer 1

Hey!

First, let's write the problem.
$12=0.9a$
Let's switch sides. This is done so that we end up with the $a$ on the left side. 
$0.9a=12$
To remove the decimal, let's multiply both sides by 10.
$0.9a\cdot \:10=12\cdot \:10$
$9a=120$
Divide both sides by 9.
$\frac{9a}{9}=\frac{120}{9}$

This tells us that our final answer would be,
$a=\frac{40}{3}$

Thanks!
-TetraFish

Answer 2

Solving for variables is easy as all we must do is isolate the variable and simplify. In this case, we need to divide "a" by 0.9 (because the variable is being multiplied by 0.9).

 12=.9a
 /.9   /.9
      
13.3=a
                                                                           
Using the math above, we can see that a=13.3.