inverse cos is the same as arc cos

so use 'acos'    

x +87 * pi ^ 3 * 43/76-91 +51 / 97 ^ 2 = sqrt (82 * 65pi)

Hi calculator353

 Is the you question or do you need to put more brackets in there somewhere?

$$x+87\pi^3*\frac{43}{76}-91+\frac{51}{97^2}=\sqrt{82*65\pi}$$

$${\frac{{\mathtt{87}}{\mathtt{\,\times\,}}{{\mathtt{\pi}}}^{{\mathtt{3}}}{\mathtt{\,\times\,}}{\mathtt{43}}}{{\mathtt{76}}}}{\mathtt{\,-\,}}{\mathtt{91}}{\mathtt{\,\small\textbf+\,}}{\frac{{\mathtt{51}}}{{{\mathtt{97}}}^{{\mathtt{2}}}}} = {\mathtt{1\,435.248\: \!592\: \!197\: \!510\: \!098\: \!2}}$$

$${\sqrt{{\mathtt{82}}{\mathtt{\,\times\,}}{\mathtt{65}}{\mathtt{\,\times\,}}{\mathtt{\pi}}}} = {\mathtt{129.401\: \!270\: \!641\: \!495\: \!6}}$$

$${\mathtt{129.401\: \!27}}{\mathtt{\,-\,}}{\mathtt{1\,435.248\: \!59}} = -{\mathtt{1\,305.847\: \!32}}$$

x= -1305.8 correct to 1 decimal place

There is a calculator on the home page.  You can do this yourself!    

I think that 64x³ is the better answer.

NOTE:  Nothing has been solved.  It has just been simplified!   

You take the 4 biggest numbers, you do not count leading zeros.  (that's 9074, you count the zero that is in the middle

0.000009074

Now you look at the 5th number, if it is 5 or bigger you round the up otherwise you do not. 

The the number is 7, it's a big one so you round up.  The last 4 becames a 5. So the answer is

0.000009075

this would be better written in scientific notation.  It is  9.075 x 10^-6

You mean in the calculator?

over is the same as divide.

1/2

there is more info on fractions with the calculator here

I don't know what the first question means but the second has  been well answered.

Thanks Aziz  

Here is a thread that will give you some ideas

you need the x on the top.

so you can either multiply both sides by x and then divide both sides by 4.5

OR

i prefer to write 4.5 as 4.5/1

And the I take the reciprocal of both sides (turn them both upside down)

You would then multiply both sides by 525.