Melody

half the base X the perpendicular height,

Here is one answer from Heureka

factor(25^2+72^2+85^2) = (2*7^3)*19

So 19 is the biggest prime.

I suppose you are supposed to do it some other way.

When you know how you can show us. 

okay.

You could have easily worked out the graphically solution from my first pic.  Did you think about it?

It always is a good idea to think before racing in.

45-13 = 32

Please proofread your question.

Are we supposed to have a value for angle B ? 

Anyway, I draw it to scale and have convinced myself that the answer is 13 degrees.

You need to work out why of course

count the zeros and that will be your answer.

Let's see,

$\sqrt{2\sqrt{8^2+15^2}+\sqrt{9^2+40^2}}\\ =\sqrt{2\sqrt{289}+\sqrt{1681}}\\ =\sqrt{2*17+41}\\ =\sqrt{34+41}\\ =\sqrt{75}\\ =5\sqrt{3}\\$

Guest just made a careless error that you should have found for yourself !

Thanks Guest.   

You need to find the 3rd angle, using the angle sum of a triangle

and then use the Sine Rule.

$\sqrt{27} - \sqrt{12}*\sqrt{300} + \sqrt{24}*\sqrt{81}\\ =\sqrt{9*3} - \sqrt{4*3}*\sqrt{100*3} + \sqrt{4*6}*9\\ =3\sqrt{3} - 2\sqrt{3}*10\sqrt{3} + 2\sqrt{6}*9\\ =3\sqrt{3} - 20\sqrt{9}+ 18\sqrt{6}\\ =3\sqrt{3} - 20*3+ 18\sqrt{6}\\ =3\sqrt{3} - 60+ 18\sqrt{6}\\$

What is a?

What is r?

What is the formula. 

Plug a and r into the formula and put it equal to 7

Then solve.