efetue:
a)
[tex] - \frac {7}{10} + \frac{1}{2} = [/tex]

b) 3,9 × 3,04=


c) 8,7÷1/2=


d)
[tex]( - \frac{42}{15} ) - ( - \frac{7}{30} )[/tex]
e)
[tex] - \frac{7}{10} \times \frac{1}{2} \div \frac{3}{5} = [/tex]
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