Why did paolo add 3(x + 2) to itself and subtract 8 page 151-152

Which expression gives the area of the triangle shown below

Lindsay used two points, (x,y; ) and (+2.82), to find the equation of the line, y = mx + b, that passes through the points. y2-y, first, she used the definition of slope and determined that the value of mis x, - . given this information, which expression must represent the value of b?

The tile along the edge of a triangular community pool needs to be replaced? ?