If the area of the triangle formed by the function y equals two-thirds of minus x plus B and the coordinate axis is 12, then B =?

If the area of the triangle formed by the function y equals two-thirds of minus x plus B and the coordinate axis is 12, then B =?

I read a wrong place before
Y = - 2 / 3x + B when x = 0, y = B when y = 0, x = 3 / 2B
That is, (B × 3 / 2b) / 2 = 12, B × 3 / 2B = 24, B × 3B = 48, 3b & sup2; = 48, B & sup2; = 16
b=±4