retour
\[\begin{aligned}
A &= \frac 23 - \frac 5 3 = \frac{2-5}3 = \frac{-3}3 = -1.&
\\
B &= \frac 4 5 + \frac 3{10} = \frac8{10}+\frac3{10} = \frac{11}{10}.&
\\
C &= \frac23 \times \frac{18}7
= \frac{2\times \overset{6}{\cancel{18}}}{\underset{1}{\cancel3}\times 7}
=\frac{12}7.&
\\
D &= 5 \div \frac 2 5 = 5\times \frac 5 2 = \frac{5\times 5}2 = \frac{25}2.&
\end{aligned}\]
retour