If we count by $3\text{'s}$ starting with $1,$ the following sequence is obtained: $1,$ $4,$ $7,$ $10,$ $\dots.$ What is the $100^\text{th}$ number in the sequence

What exactly is your question?

First step is to get rid of the square root. remember that a square root is the same as raising to the (1/2) power. see below: multiply exponents per exponent rules to get: remember you subtract exponents from the denominator and add exponents in the numerator so: simplify further: so a is the correct choice. if you don't understand this google exponent rules and it will you understand. look at the image results.