Answer:
230 were sold at the door
170 were sold in advance
Step-by-step explanation:
x=at door y=in advance
x+y=400
3x+2y=1030
y=-x+400
2y=-3x+1030
y=-3/2x+515
-x+400=-3/2x+515
x=230 y=170
The given equation is: 
To find the line perpendicular to it, we interchange coefficients and switch the signs of one coefficient.
The equation to a line perpendicular to it is:
$ 2y-x=c$
where, $c$ is some constant we have determine using the condition given.
It passes through $(2,-1)$
Put the point in our equation:
$2(-1)-(2)=c$
$c=-2-2$
$c=-4$
The final equation is:
$\boxed{ 2y-x=-4}$
<span>To rewrite the expression as a multiple of a sum of two numbers with no common factor, we're supposed to find the greatest common factor between the terms and factor it out. </span>We can see that both 15 and 24 are divisible by 3. So let's factor the 3 out. Since the 3 goes into 15 five times and into 24 eight times, the expression can be rewritten like this.
15 + 24 = 3(5 + 8)
the answer for this question is 64-144a+108a^2-27a^3
