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$\frac{2a}{ {a}^{2} - 25 {b}^{2} } - \frac{2}{a + 5b} = \frac{2a - 2(a - 5b)}{ {a}^{2} - 25 {b}^{2} } = \frac{2a - 2a + 10b}{a ^{2} - 25 {b}^{2} } = \frac{10b}{ {a ^{2} - 25 {b}^{2}} }$
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$\frac{7a}{a ^{2} - 4 {b}^{2} } - \frac{7}{a - 2b} = \frac{7a - 7(a + 2b)}{ {a}^{2} - 4 {b}^{2} } = \frac{7a - 7a - 14b}{ {a}^{2} - 4 {b}^{2} } = - \frac{14b}{a ^{2} - 4 {b}^{2} }$
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$\frac{4a}{ {a ^{2} - 64b}^{2} } - \frac{4}{a + 8b} = \frac{4a - 4(a - 8b)}{ {a}^{2} - 64 {b}^{2} } = \frac{4a - 4a + 32b}{ {a}^{2} - 64 {b}^{2} } = \frac{32b}{ {a}^{2} - 64 {b}^{2} }$