Alan

Here's how you could go about answering this:

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Rewrite this as y = (1/2)x - 4, then perpendicular lines will have equations of the form 

y = -2x + k, where k is a constant (different lines will have different values of k).

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"what i'm trying to say is, does the sign of multiplication "*" affect the precedence of equation?"

No. Implicit multiplication (I.e. multiplication without an explicit *) is still multiplication.

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As follows: \(\sqrt{y^5} \rightarrow \sqrt{y^4\times y} \rightarrow y^2\sqrt y\)

The App was a one off payment (I've certainly never paid more than once!).

And yes, the image was done just using the iPad's screen capture facility.

I paid for the app on my iPad!

Here's Wolfram Alpha's solution:

You can use Heron's formula:

Let s = semi-perimeter     s = (12 + 14 + 16)/2 → 21 cm

Area = sqrt(s*(s-a)*(s-b)*(s-c))

Area = sqrt(21*(21 - 12)*(21 - 14)*(21 - 16)) cm²

Area = sqrt(21*9*7*5) → 81.3 cm² 

If this is 3*(x^2)*(y^5)/(9*(x^7)*y) then we have (y^(5-1))/(3*(x^(7-2)) → y^4/(3*x^5)