Помогите пожалуйста сделать 71 ( и если не сложно объясните)❤

71)
1)
$\frac{ {a}^{2} - 32 }{4a + 40} - \frac{68}{4a + 40} = \frac{ {a}^{2} - 32 - 68}{4a + 40} = \frac{ {a}^{2} - 100 }{4(a + 10)} = \frac{(a - 10)(a + 10)}{4(a + 10)} = \frac{a - 10}{4} = \frac{12.12 - 10}{4} = \frac{2.12}{4} = 0.53$
2)
$\frac{ {x}^{2} + 3x }{ {x}^{2} - 49 } + \frac{17x - 49}{49 - {x}^{2} } = \frac{ {x}^{2} + 3x }{ {x}^{2} - 49 } - \frac{17x - 49}{{x}^{2} - 49 } = \frac{ {x}^{2} + 3x - (17x - 49)}{ {x}^{2} - 49} = \frac{ {x}^{2} + 3x - 17 x+ 49 }{ {x}^{2} - 49 } = \frac{ {x}^{2} - 14x + 49}{ {x}^{2} - 49 } = \frac{ {(x - 7)}^{2} }{(x - 7)(x + 7)} = \frac{x - 7}{x + 7} = \frac{ - 6.9 - 7}{ - 6.9 + 7} = \frac{ - 13.9}{0.1} = - 139$