`#3107.101107`
`2)`
`E = 1/13 + (-5/18 - 1/13 + 12/17) - (12/17 - 5/18 + 7/5)`
`= 1/13 - 5/18 - 1/13 + 12/17 - 12/17 + 5/18 - 7/5`
`= (1/13 - 1/13) + (5/18 - 5/18) + (12/17 - 12/17) - 7/5`
`= -7/5`
`3)`
`F = 15/14 - (17/23 - 80/87 + 5/4) + (17/23 -15/14 + 1/4)`
`= 15/14 - 17/23 + 80/87 - 5/4 + 17/23 - 15/14 + 1/4`
`= (15/14 - 15/14) - (17/23 - 17/23) - (5/4 - 1/4) + 80/87`
`= -4/4 + 80/87`
`= -1 + 80/87 = -7/87`
`4)`
\(G=\dfrac{1}{25}-\dfrac{4}{27}+\left(-\dfrac{23}{27}-\dfrac{1}{25}-\dfrac{5}{43}\right)+\dfrac{5}{43}-\dfrac{4}{7}\)
`= 1/25 - 4/27 - 23/27 - 1/25 - 5/43 + 5/43 - 4/7`
`= (1/25 - 1/25) - (4/27 + 23/27) - (5/43 - 5/43) - 4/7`
`= -27/27 - 4/7`
`= -1 - 4/7`
`= -3/7`
