What is the first step to finding the equation of a line when 2 points are known?

What is the value of x in the this question ?

The roots of the function f(x) = x2 – 2x – 3 are shown. what is the missing number?

At the county fair, the baxter family bought 6 hot dogs and 4 juice drinks for $12.90. the farley family bought 3 hot dogs and 4 juice drinks for $8.55. find the price of a hot dog and the price of a juice drink.