In total, the part of the job completed was 3/4+2/9=27/36+8/36 (using 9*4=36 as the lowest common denominator of 4 and 9, allowing us to express the two fractions as multiples of a 36th: 3/4=27/36=3*9/(4*9) and 2/9=8/36=2*4/(9*4)). So we add the fractions together (27+8)/36=35/36. That leaves (36-35)/36=1/36 of the job to be done.