1) 6•(2/3a+5/12b) =6*2/3a + 6*5/12b = 3*2*2/3a + 6*5/(6*2b) = 4/a + 5/2b = (4*2b + 5*a)/(2ab) =(8b+5a)/(2ab)
2)1/3•(9/11m-6/7n) = 
3) 12•(3/4x+13/18y-1/24z) = (12*3)/4x + (12*13)/18y - (12*1)/24z = (4*3*3)/4x + (6*2*13)/(6*3y) - 12/(12*2z) = 9/x + 26/3y - 1/2z
4) 1 1/7*(7p+21/24q-1 3/4) = (7+1)/7 *(7p + 21/24q - (4+3)/4) = 8/7 *(7p + 21/24q - 7/4) = 8*7p/7 + (21*8)/(7*24q) - 7*8/(7*4) = 8p + (7*3*8)/(7*3*8*q) - 2*4/4 = 8p + 1/q -2