Does anyone know the answer to this?

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

What is the value of x when x + 7 = 21?

Asystem of equations has 1 solution.if 4x-y=5 is one of the equations , which could be the other equation ?