a) \({1 \over 3} + {3 \over 8} - {7 \over {12}} =\frac{8}{24}+\frac{9}{24}-\frac{14}{24}= {{8 + 9 - 14} \over {24}} = {3 \over {24}} = {1 \over 8}\)

b) \({{ - 3} \over {14}} + {5 \over 8} - {1 \over 2} =\frac{-12}{56}+\frac{35}{56}-\frac{28}{56}= {{ - 12 + 35 - 28} \over {56}} = {{ - 5} \over {56}}\)

c) \({1 \over 4} - {2 \over 3} - {{11} \over {18}} =\frac{9}{36}-\frac{24}{36}-\frac{22}{36}= {{9 - 24 - 22} \over {36}} = {{ - 37} \over {36}}\)

d) \({1 \over 4} + {5 \over {12}} - {1 \over {13}} - {7 \over 8} \)

\(=\frac{78}{312}+\frac{130}{312}-\frac{24}{312}-\frac{273}{312}\)

\( = {{78 + 130 - 24 - 273} \over {312}} \)

\(= {{208 - 297} \over {312}} = {{ - 89} \over {312}}\)