\({3 \over 5 a} - {2 \over 5 a} = {1 \over 5 a}\)

\({9 \over a} + {3 \over 4 a} = {36 \over 4 a} + {3 \over 4 a} = {39 \over 4 a}\)

\({4 \over 7 x} + {2 \over 6 y} = {24 y \over 42 x y} + {14 x \over 42 x y} = {24 y + 14 x \over 42 x y} = {12 y + 7 x \over 21 x y}\)

\(9 - {4 \over 7 x} = {9 \over 1} - {4 \over 7 x} = {63 x \over 7 x} - {4 \over 7 x} = {63 x - 4 \over 7 x}\)

\(3 p - {7 \over 8 p} = {3 p \over 1} ⋅ {8 p \over 8 p} - {7 \over 8 p} = {24 p^{2} \over 8 p} - {7 \over 8 p} = {24 p^{2} - 7 \over 8 p}\)

\({3 p \over q} + {7 \over 5 q} = {15 p \over 5 q} + {7 \over 5 q} = {15 p + 7 \over 5 q}\)

\({3 b \over 9 a} - {5 a \over 4 b} = {12 b^{2} \over 36 a b} - {45 a^{2} \over 36 a b} = {-45 a^{2} + 12 b^{2} \over 36 a b} = {-15 a^{2} + 4 b^{2} \over 12 a b}\)

\({5 x \over x} = {5 \over 1} = 5\)

\({a \over 6 a} = {1 \over 6}\)

\({-8 x \over 28 x} = -\frac{2}{7}\)

\({-16 a \over 2 a} = -8\)

\({18 x y \over 21 x z} = {6 y \over 7 z}\)

\({-18 q \over 21 p q} = -{6 \over 7 p}\)

\({8 x y z \over 4 y z} = 2 x\)

\({3 a b \over b} + {2 a c \over c} = 3 a + 2 a = 5 a\)

\({9 \over x} ⋅ {4 \over y} = {36 \over x y}\)

\({x \over 9} ⋅ -{7 \over y} = -{7 x \over 9 y}\)

\(-{2 \over 9} ⋅ p = -{2 p \over 9}\)

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

\({6 \over 7} : a = {6 \over 7} : {a \over 1} = {6 \over 7} ⋅ {1 \over a} = {6 \over 7 a}\)

\({8 a \over 9} + {a + 6 \over 2} = {16 a \over 18} + {9 (a + 6) \over 18} = {16 a + 9 (a + 6) \over 18} = {25 a + 54 \over 18}\)

\(-{2 \over 9} : {p + 3 q \over q} = -{2 \over 9} ⋅ {q \over p + 3 q} = -{2 q \over 9 (p + 3 q)} = -{2 q \over 9 p + 27 q}\)

\({2 a - 4 \over -3 a - 9} + 6 = {2 a - 4 \over -3 a - 9} - {-6 (-3 a - 9) \over -3 a - 9} = {2 a - 4 + 6 (-3 a - 9) \over -3 a - 9} = {2 a - 4 - 18 a - 54 \over -3 a - 9} = {-16 a - 58 \over -3 a - 9}\)