Question

atividade resolva as contas mmc​

Answer 1

Resposta:

a)

$x - \dfrac{x}{7} = - 3 \\ \\ \dfrac{7 \times x - x = 7 \times ( - 3)}{7} \\ \\ 7x - x = - 21 \\ \\ 6x = - 21 \\ \\ x = - \dfrac{21÷3}{6÷3} \\ \\ \green{- \dfrac{7}{2}}$

b)

$\dfrac{x}{5} + \dfrac{x}{2} = 21 \\ \\ \frac{2x + 5x = 10 \times 21}{10} \\ \\ 2x + 5x = 10 \times 21 \\ \\ 7x = 210 \\ \\ x = \dfrac{210}{7} \\ \\ \green{x = 30}$

c)

$\frac{5}{7} - 3x = 5 \\ \\ \dfrac{1 \times 5 - 7 \times 3x = 7 \times 5}{7} \\ \\ 5 - 21x = 35 \\ \\ 5 - 35 = 21x \\ \\ -30 = 21x \\ \\ x = \dfrac{-30 \div 3}{21 \div 3} \\ \\ \green{x = - \dfrac{10}{7} }$

Bons Estudos!