A number with an exponent (b^e) consists of a base (b) raised to a power (e). The exponent indicates the number of times that the base is multiplied by itself. A base with an exponent of 1 equals the base (b¹ = b) and a base with an exponent of 0 equals 1 ( (b⁰ = 1).

A prime number is an integer greater than 1 that has no factors other than 1 and itself. Examples of prime numbers include 2, 3, 5, 7, and 11.

There are 3 4-passenger taxis available so that's 3 x 4 = 12 total seats. There are 15 people needing transportation leaving 15 - 12 = 3 who will have to find other transportation.

Use PEMDAS (Parentheses, Exponents, Multipy/Divide, Add/Subtract):

2 + (5 + 5) ÷ 5 x 2 - 4²
P: 2 + (10) ÷ 5 x 2 - 4²
E: 2 + 10 ÷ 5 x 2 - 16
MD: 2 + \( \frac{10}{5} \) x 2 - 16
MD: 2 + \( \frac{20}{5} \) - 16
AS: \( \frac{10}{5} \) + \( \frac{20}{5} \) - 16
AS: \( \frac{30}{5} \) - 16
AS: \( \frac{30 - 80}{5} \)
\( \frac{-50}{5} \)
-10

A number in scientific notation has the format 0.000 x 10^exponent. To convert to scientific notation, move the decimal point to the right or the left until the number is a decimal between 1 and 10. The exponent of the 10 is the number of places you moved the decimal point and is positive if you moved the decimal point to the left and negative if you moved it to the right:

0.000068 in scientific notation is 6.8 x 10^-5