Don't worry, the right ones won't leave.
1,
B=$\frac{13}{15}$ .0,25.3+($\frac{8}{15}$ - 1 $\frac{19}{60}$ ) : 1 $\frac{23}{24}$
= $\frac{13}{15}$ .$\frac{1}{4}$ .3+($\frac{8}{15}$ -$\frac{79}{60}$ ) :$\frac{47}{24}$
=$\frac{13}{60}$ .3+($\frac{-47}{60}$ .$\frac{24}{47}$
= $\frac{13}{20}$ +$\frac{-2}{5}$
= $\frac{1}{4}$
2,
5,2.x +7$\frac{2}{5}$=6$\frac{3}{4}$
5,2 .x = 6$\frac{3}{4}$-7$\frac{2}{5}$
5,2.x = $\frac{-13}{20}$
x =$\frac{-13}{20}$:5,2
x = $\frac{-1}{8}$
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