A) 1/2-(1/3+1/10) B) 1/12-(-1/6-1/4) C) 1/2--1/3+1/23+1/6

$a.\dfrac{1}{2}-\bigg(\dfrac{1}{3}+\dfrac{1}{10}\bigg) \\=\dfrac{15}{30}-\bigg(\dfrac{10}{30}+\dfrac{3}{30}\bigg) \\=\dfrac{15}{30}-\dfrac{13}{30} \\=\dfrac{1}{15} \\b.\dfrac{1}{12}-\bigg(\dfrac{-1}{6}-\dfrac{1}{4}\bigg) \\=\dfrac{2}{24}-\bigg(\dfrac{-4}{24}-\dfrac{6}{24}\bigg) \\=\dfrac{2}{24}-\dfrac{-10}{24} \\=\dfrac{1}{2} \\c.\dfrac{1}{2}-\dfrac{-1}{3}+\dfrac{1}{23}+\dfrac{1}{6} \\=\dfrac{69}{138}-\dfrac{-46}{138}+\dfrac{6}{138}+\dfrac{23}{138} \\=\dfrac{144}{138}=\dfrac{24}{23}$