Question

Решите 2/3(10с)=-8 2t=1 1/3(t+5) 1 1/4(x-2)=-5(x+1) это 7 класс дрофеев №389(г,д,е)

Answer 1

$\frac{2}{3} (10c) = - 8 \\ \\ \frac{20}{3} c = - 8 \\ \\ c = - 8 \div \frac{20}{3} \\ \\ x = - \frac{5}{6}$

$2t = 1 \frac{1}{3} (t + 5) \\ \\ 2t = 1 \frac{1}{3} t + 6 \frac{1}{3} \\ \\ 2t - 1 \frac{1}{3} t = 6 \frac{1}{3} \\ \\ \frac{2}{3} t = 6 \frac{1}{3} \\ \\ t = 6\frac{1}{3} \div \frac{2}{3} \\ \\ t = 9 \frac{1}{2} \\ \\ t = 9.5$

$1 \frac{1}{4} (x - 2) = - 5(x + 1) \\ \\ 1 \frac{1}{4} x - 2 \frac{1}{2} = - 5x - 5 \\ \\ 1 \frac{1}{4} x + 5x = - 5 + 2 \frac{1}{2} \\ \\ 6 .25x = - 2.5 \\ \\ x = - 2.5 \div 6.25 \\ \\ x = - 0.4$