what does x represent

What is the equation in point slope form of the line that passes through the point (-1, -3) and has a slope of 4? y-1=4(x-3) or y+3=4(x+1)

How can we find the measure of an exterior angle if we know the measurement of an interior angle

Twenty-five percent of the customers entering a grocery store between 5 p.m. and 7 p.m. use an express checkout. consider five randomly selected customers, and let x denote the number among the five who use the express checkout.