# Thread: Been a while, need a little help

1. ## Been a while, need a little help

It has been a long time since math classes, however I need some algebra for a website I am working on. I am pretty much lost as how to get the number I need. So, here is an equation I am trying to solve:

D = B x .80

A = 120 + B + (D x 2) + ((D x.80) x 2)

I am absolutely horrible with explanations so I made a diagram explaining what I am trying to accomplish.

I need a solution in the form of B = A ......... I will know what A is at runtime, so if I can find a function I can create B and then create the rest of the objects. The problem is that A will change based on the users screen size, so I need a function like this to come up with B based on that.

Thanks for any help, i'm pretty lost on this one.

2. D = B x .80

A = 120 + B + (D x 2) + ((D x.80) x 2)

solving for B...

1st eliminate D
A = 120 + B + ((B x .80) x 2) + ((B x .80) x 2)
2nd eliminate inner parenthesis
A = 120 + B + (B x 1.6) + (B x 1.6)
3rd combine
A = 120 + B + 2(B x 1.6)
4th expand
A = 120 + B + 2B x 3.2
5th put together like terms
A = 3B + 123.2
and then basic algebra
3B = A - 123.2
B = (A - 123.2) / 3
and thats it!

3. I appreciate the quick reply, and I think that it's really close. The only thing I noticed was in the first step where you plug B x .80 into for D.

The second set of boxes is reduced 20% from the first set, which is reduced 20% from B.

So I think with the D's eliminated it would look like

A = 120 + B + ((B x .80) x 2) + (((B x .80) x .80) x 2)

I came up with this (with help from you on how to eliminate the extra parenthesis)

A = 120 + B + ((B x .80) x 2) + (((B x .80) x .80) x 2)

A = 120 + B + (2B x 1.6) + ((.8B x .64) x 2)

A = 120 + B + (2B x 1.6) + (1.6B x 1.28)

Not sure where to go from there, and not 100% sure thats right. How do I add the two functions in the parenthesis together so I can start solving for B?

Thanks again!

[edit 2]

I tried again, and I continued working on the problem, although the numbers I got don't seem to logically be possible.

From the starting point above:

A = 120 + B + 3.2B + 2.048B

A = 120 + 6.248B

A - 120 / 6.248 = B

The 6.248 seems really inflated, i'm not very sure it's correct.

[edit 3]

I ran some numbers through the function that I got, and it spits out to low of a value for B, i'm just not sure where I messed up.

[edit 4]

I fixed it!! I did the distribution wrong, I looked at how you did it again and I got the function working!

I am curious though, for example ((B x .80) x 2) why do you not distribute the 2 to the B as well as the .80?

4. A = 120 + B + (2B x 1.6) + (1.6B x 1.28)

think of it as
A = 120 + B + (2 x B x 1.6) + (1.6 x B x 1.28)
so..
A = 120 + B + (2 x B x 1.6) + (1.6 x B x 1.28)
A = 120 + B + (3.2 x B) + (2.05 x B)
then you can add the similar terms together
A = 120 + B(1 + 3.2 + 2.05)
A = 120 + 6.25 x B

then simple algebra from there like last time.