solve for x and y

a) (x/3) + (y/4) = 11

(5x/6) - (y/3) + 7 =0

b) 6x + 5y = 7x + 3y + 1 = 2(x + 6y -1)

c) [( x + y - 8 )/2] = [ (x + 2y -14) / 3] = [ ( 3x + y - 12) /11]

d) [(bx)/a] - [(ay)/b] + a + b = 0

bx - ay + 2ab = 0

now add all the values of x an y (i can do this part by myself)

thnx in advance