How to make an equation when pie chart angle redrawn? 
I tried to solve like this, the actual answer is 36. I am getting 44.

 A: Your original equation setup is wrong.
let $x$ be the original number of Plain Crisps and $y$ be the total original number of crisps.
$x = y/4$
$x - 4 = (y - 4)/6$
are your equations. Thus you have
$(y - 16)/4 = (y-4)/6 \implies 3y - 48 = 2y - 8 \implies y = 40$
Thus afterward, you have $40 - 4 = 36$ packets.
A: You can do it with just one variable, $x,$ but you have to make up your mind what $x$ stands for.
In the equations you wrote, on the left side you seem to be saying that $x$ is the original total number of packets in the cupboard, and $\frac14$ of this amount is the original number of packets of plain crisps.
On the right side you seem to be saying that $x$ is the total number of packets after Marco eats the four packets, and $\frac16$ of that number are packets of plain crisps.
You add four on the right-hand side because there are four more packets of plain crisps on the left hand side than on the right.
The error is that $x$ means something different on the right from what it means on the left.
Let's say $x$ is the total number of packets remaining after Marco eats four packets. That's convenient since as soon as we find $x,$ we can give it as the answer.
Then before Marco ate four packets, there were $x + 4$ packets. So $x + 4,$ not $x,$ should be in the numerator on the left side of the equation:
$$
\frac{x+4}{4} = \frac x6 + 4.
$$
Start with this and solve for $x,$ and if you perform the remaining steps correctly you will get the correct answer.
