Alan

Look carefully at the information you have in the diagram.  With O as the centre of the circle and a right-angle at R, then length PR is half of length PQ, so PR is 10.  This means you have a right-angled triangle with hypotenuse of length 12, one side of length 10 and one of length x.  From Pythagoras we know that:

x² + 10² = 12².   Can you take it from there?

Ok, no need to - Melody's already done it!!  Apart from expressing the answer as a decimal rounded to two places.

Right idea NinjaDevo, but you need to take care in the implementation.

Your solution to part 1 is correct only if the questioner meant b = (w - z)/v.  If the question is really as written, namely,

b = w - z/v, then one simply adds z/v to both sides to get w = b + z/v.

For part 2 you must divide every term by r, so b/r = r*w/r + r/r  or b/r = w + 1; subtract 1 from both sides to get

w = b/r - 1.

Rose has interpreted this correctly exactly as it is written:

8.2*105*(7.7*10 - 1) or 861*(77 - 1) or 861*76 or 65436.

However, it's just possible it was meant to be 8.2*10⁵*7.7*10^-1, in which case it is 63.14*10⁴ or 6.314*10⁵.

Mind you, I've no strong reason for thinking this other than that the -1 in the second set of brackets looks like it wants to be an exponent!!

8x + y = -16    ...(1)

-3x + y = -5    ...(2)

Subtract 8x from both sides of (1) to get

y = -16 - 8x    ...(3)

Now eliminate y from (2) by replacing it with the right-hand side of (3)

-3x -16 -8x = -5

Collect the x terms

-11x -16 = -5

Add 16 to both sides

-11x = 11

Divide both sides by -11

x = -1 

Now eliminate x from (3) to find y

y = -16 -8*(-1)

y = -8

Check by putting the values for x and y back into (1)

8*(-1) + (-8) = -16  ok

and (2)

-3*(-1) + (-8) = -5  ok

Division by zero is not allowed in mathematics.  The calculator is correct to say it is an error. 

If a township is divided into 36 squares, each 1 mile on a side, then the township is just 36 square miles (36*640 acres).  

If the question was meant to say a township consisted of a square 36 miles on a side, then NinjaDevo's answer is correct. 

175 = 25*7 so √175 = √(25*7) = √25 * √7 = 5*√7 ≈ 13.23

$$2^{2013}\approx9.4\times10^{605}$$

There are 606 digits in all.  This is what 2²⁰¹³ is in full: