Make b the subject of formula

Which matrix multiplication is possible?

Which formula finds the probability that a point on the grid below will be in the blue area? p(blue) = total number of squares number of blue squares number of blue squares p(blue) = total number of squares number of blue squares p(blue) = number of white squares

You paint a 1/2 of a wall in 1/4 hour. how long will it take you to paint one wall