I was wondering is there a way to calculate some number that involve percentage backward.
For example
$10 + (10\times 0.2) + (10\times 0.06) = 12.6$
If I was given $12.6$, how should I calculate it back to $10$? For example, how do I get the $A$ such that $A + (A\times 0.2) + (A\times 0.06) = 12.6$?
If you are given the equation $A+(A\times 0.2)+(A\times 0.06)=12.6$ and want to solve for $A$, you can use middle-school algebra to simply combine all of the terms on the left by adding.
You have then $A+(A\times 0.2)+(A\times 0.06)=A\times (1+0.2+0.06)=1.26\times A=12.6$, at which point you can divide by $1.26$ to get $A=10$.