Ihave 4 math questions that i don't understand. ! ?
b^-3=1/216 b=?
743.8 × 103=?
36 ÷ 10–3=?
what is (2.1 × 103) × (4 × 10–7)?

-- A negative exponent means the number is in the denominator.
    b⁻³  means  1/b³ .
   So  1/b³ = 1/216 .                      You can do it now.

-- If that number is " 10³ ", it means 1,000 .
   If that number is " 103 " and you can't remember
   how to do multiplication with a pencil, then you'll
   have to use your calculator.

-- Again ...  10⁻³  means  1/10³  or  1/1000 .
   So the problem is really  36 divided by  1/1000 .
   Be very careful.  That means  36 x 1000 .

-- To multiply powers that have the same base,
   you add the exponents.

   Example:    10⁴  times  10⁵  =  10⁹ .

   This question can be rearranged as      (2.1 x 4) x (10³ x 10⁻⁷)

                                                                 (10³)  times  (10⁻⁷)   is  10⁻⁴  .