Tetration

How about: 

4 + √4 +√4 +√4

Technically speaking you've used two's since √x = ²√x

The expression is ambiguous, but I'll assume you mean:

$$\frac{3/4(-8)}{2-3}$$  

The order of operations are: 

1. Solve what's in the paranthesis

2. Multiply (*) and divide (:)

3. Add (+) ans subtract (-)

We get:

$$\frac{3/4(-8)}{2-3} = \frac{3/-32}{-1}$$

Multiply both the numerator (top) and denominator (bottom) with -1

$$\frac{3/32}{1}=3/32 = 0.09375$$

IV in Roman notation ;)

2^-1 = 1/2 = 0,5

Did that help ?

U r welcome :)

d = 13       C = ?

Remember the formula:

$$C = pi*d$$

So we get: 

C ≈ 3,14* 13 = 40,82

C ≈ 40,82

2x +3y = 34 

2x + 3(5x) = 34  (from y = 5x)

2x + 15x = 34

17x = 34 

x = 2

y = 5x

y= 10

0.0016931 = 1.6931* 10^-3.

So we get:

(1.6931* 10^-3)(10⁶) = 1.6931* 10^6-3 = 1.6931* 10³ = 1693,1

Scientific notation is on the form: a*10^b.

Dispose of all the trailing zeroes, and set the period after one single digit: We get: a = 4.81

The exponent is one less than the number of digits. Therefore, "b" is 13.

So we get: 4,81 * 10¹³

Do you mean?:

$$(6*7)(\frac{1}{7})$$

We see that one of the factors is equal to the denominator (bottom) in the fraction. They cancel out, and we get:

(6*7)(1/7) = (6*1)(1/1) = 6