\({5 \over 8 a} + {7 \over 8 a} = {12 \over 8 a} = {3 \over 2 a}\)

\({2 \over x} - {4 \over 6 x} = {12 \over 6 x} - {4 \over 6 x} = {8 \over 6 x} = {4 \over 3 x}\)

\({2 \over 5 p} - {9 \over 8 q} = {16 q \over 40 p q} - {45 p \over 40 p q} = {16 q - 45 p \over 40 p q}\)

\(9 - {8 \over 3 a} = {9 \over 1} - {8 \over 3 a} = {27 a \over 3 a} - {8 \over 3 a} = {27 a - 8 \over 3 a}\)

\(2 x - {9 \over 7 x} = {2 x \over 1} ⋅ {7 x \over 7 x} - {9 \over 7 x} = {14 x^{2} \over 7 x} - {9 \over 7 x} = {14 x^{2} - 9 \over 7 x}\)

\({6 p \over q} - {8 \over 7 q} = {42 p \over 7 q} - {8 \over 7 q} = {42 p - 8 \over 7 q}\)

\({6 b \over 4 a} - {5 a \over 9 b} = {54 b^{2} \over 36 a b} - {20 a^{2} \over 36 a b} = {-20 a^{2} + 54 b^{2} \over 36 a b} = {-10 a^{2} + 27 b^{2} \over 18 a b}\)

\({4 x \over x} = {4 \over 1} = 4\)

\({x \over 3 x} = {1 \over 3}\)

\({21 a \over -24 a} = -\frac{7}{8}\)

\({18 a \over 2 a} = 9\)

\({-6 x y \over 10 x z} = -{3 y \over 5 z}\)

\({-28 b \over 32 a b} = -{7 \over 8 a}\)

\({-9 p q r \over 3 q r} = -3 p\)

\({7 x y \over y} + {6 x z \over z} = 7 x + 6 x = 13 x\)

\({3 \over a} ⋅ -{9 \over b} = -{27 \over a b}\)

\({x \over 7} ⋅ -{6 \over y} = -{6 x \over 7 y}\)

\({6 \over 5} ⋅ a = {6 a \over 5}\)

\({4 \over x} : {9 \over y} = {4 \over x} ⋅ {y \over 9} = {4 y \over 9 x}\)

\(-{4 \over 3} : p = -{4 \over 3} : {p \over 1} = -{4 \over 3} ⋅ {1 \over p} = -{4 \over 3 p}\)