Hitung lah nilai b,jika garis yg menghubungkan titik (3b,7) dan (-11,5b) bergradien -3

m = ( y2 - y1 ) / ( x2 - x1)
- 3 = ( 5b - 7 ) / ( - 11 - 3b)
- 3 ( - 11 - 3b ) = 5b - 7
33 + 9b = 5b - 7
9b - 5b = - 7 - 33
4b = - 40
b = - 10