与えられた9つの計算問題を解く。

1. 問題の内容

与えられた9つの計算問題を解く。

2. 解き方の手順

(1) $-2x \times 9 = -18x$

(2) $6a \div (-8) = \frac{6a}{-8} = -\frac{3}{4}a$

(3) $-\frac{2}{3}x \div \left(-\frac{4}{15}\right) = -\frac{2}{3}x \times \left(-\frac{15}{4}\right) = \frac{2 \times 15}{3 \times 4}x = \frac{30}{12}x = \frac{5}{2}x$

(4) $5(3a - 1) = 5 \times 3a - 5 \times 1 = 15a - 5$

(5) $(4a - 5) \times (-6) = 4a \times (-6) - 5 \times (-6) = -24a + 30$

(6) $(8a - 20) \times \frac{3}{4} = 8a \times \frac{3}{4} - 20 \times \frac{3}{4} = 6a - 15$

(7) $12\left(\frac{5}{6}x + \frac{1}{4}\right) = 12 \times \frac{5}{6}x + 12 \times \frac{1}{4} = 10x + 3$

(8) $(45a - 5) \div 5 = \frac{45a}{5} - \frac{5}{5} = 9a - 1$

(9) $(6 - 9x) \div \left(-\frac{3}{2}\right) = (6 - 9x) \times \left(-\frac{2}{3}\right) = 6 \times \left(-\frac{2}{3}\right) - 9x \times \left(-\frac{2}{3}\right) = -4 + 6x = 6x - 4$

3. 最終的な答え

(1) $-18x$

(2) $-\frac{3}{4}a$

(3) $\frac{5}{2}x$

(4) $15a - 5$

(5) $-24a + 30$

(6) $6a - 15$

(7) $10x + 3$

(8) $9a - 1$

(9) $6x - 4$