a) P= 2/3--1/4+3/5-7/45--5/9+1/12+1/35=(2/3+1/4+1/12)+(3/5-7/45+1/35)+5/9=1+4/9+1/35=1+4/9+5/9+1/35=1+1+1/35=71/35

b)Q=(5-6-2)+(-3/4-7/4+5/4)+(1/5+8/5-16/5)=-(3+5/4+7/5)=113/20

a) A= 1/3-8/15-1/7+2/3-7/15+8/7=(1/3+2/3)+(8/7-1/7)-(8/15+7/15)=1+1-1=1

b) B= 1/4+3/5-1/8+2/5-5/4=(1/4-5/4)+(3/5+2/5)-1/8=-1+1-1/8=-1/8

a)  \(\frac{2}{3}.\frac{5}{4}-\frac{3}{4}.\frac{2}{3}=\frac{2}{3}\left(\frac{5}{4}-\frac{3}{4}\right)=\frac{2}{3}\frac{.1}{4}\) = \(\frac13\)

b) \(2.\left(\left(\right.\frac{- 3}{2}\left.\right)\right)^2-\frac{7}{2}=2.\left(\frac94\right)-\frac72=\frac21.\frac94-\frac72=\frac92-\frac72=\frac22=1\)

c) \(-\frac{3}{4}.5\frac{3}{13}-0,75.\frac{36}{13}=-\frac34.\frac{68}{13}-\frac34\frac{.36}{13}=-\frac34\left(\frac{68}{13}+\frac{36}{13}\right)=-\frac34\frac{.104}{13}=-6\).