与えられた数学の問題集の中から、指定された問題（今回はすべて）を解き、最終的な答えを求める問題です。

1. 問題の内容

与えられた数学の問題集の中から、指定された問題（今回はすべて）を解き、最終的な答えを求める問題です。

2. 解き方の手順

問題1：式の計算

(1) $3x-5y-6x-y = (3-6)x + (-5-1)y = -3x - 6y$

(2) $-y^2 + 9y - 4y - 4y^2 = (-1-4)y^2 + (9-4)y = -5y^2 + 5y$

(3) $(2a-b)+(13a-3b) = (2+13)a + (-1-3)b = 15a - 4b$

(4) $(26x-42y)-(27x-21y) = (26-27)x + (-42+21)y = -x - 21y$

(5) $8(x+3y)+2(-7x+10y) = 8x+24y-14x+20y = (8-14)x + (24+20)y = -6x + 44y$

(6) $12(2m-4n)-14(m-2n-1) = 24m - 48n - 14m + 28n + 14 = (24-14)m + (-48+28)n + 14 = 10m - 20n + 14$

(7) $(1.6a^2+2a)-0.3(a-8a^2) = 1.6a^2 + 2a - 0.3a + 2.4a^2 = (1.6+2.4)a^2 + (2-0.3)a = 4a^2 + 1.7a$

(8) $\frac{2}{3}(6x-3y) + \frac{1}{9}(6x-9y) = 4x-2y + \frac{2}{3}x - y = (4 + \frac{2}{3})x + (-2-1)y = \frac{14}{3}x - 3y$

(9) $\frac{3a+2b}{4} - \frac{a-7b}{6} = \frac{3(3a+2b) - 2(a-7b)}{12} = \frac{9a+6b-2a+14b}{12} = \frac{7a+20b}{12}$

(10) $(-5m) \times 10n = -50mn$

(11) $-18ab \div 2a = \frac{-18ab}{2a} = -9b$

(12) $5xy \times (-42y) \div (-3x) = \frac{5xy \times (-42y)}{-3x} = \frac{-210xy^2}{-3x} = 70y^2$

(13) $-\frac{a^2x}{8} \div (-\frac{3}{56}ax^2) \div (-\frac{7}{x}) = -\frac{a^2x}{8} \times (-\frac{56}{3ax^2}) \times (-\frac{x}{7}) = -\frac{a^2x \times 56 \times x}{8 \times 3ax^2 \times 7} = -\frac{56a^2x^2}{168ax^2} = -\frac{a}{3}$

(14) $3y \times (-2x)^3 = 3y \times (-8x^3) = -24x^3y$

問題2：式の値

(1) $x=-11, y=-2$のとき、$(17x+y) - (21x-6y) = 17x+y-21x+6y = (17-21)x + (1+6)y = -4x + 7y = -4(-11) + 7(-2) = 44 - 14 = 30$

(2) $x=2.2, y=0.4$のとき、$10(2x-3y) + 5(-x+4y) = 20x - 30y - 5x + 20y = (20-5)x + (-30+20)y = 15x - 10y = 15(2.2) - 10(0.4) = 33 - 4 = 29$

(3) $x=\frac{5}{14}, y=-\frac{1}{4}$のとき、$-\frac{12}{x} \div \frac{xy}{7} \times (-\frac{x^2y^3}{3}) = -\frac{12}{x} \times \frac{7}{xy} \times (-\frac{x^2y^3}{3}) = \frac{12 \times 7 \times x^2y^3}{x \times xy \times 3} = \frac{84x^2y^3}{3x^2y} = 28y^2 = 28(-\frac{1}{4})^2 = 28 \times \frac{1}{16} = \frac{28}{16} = \frac{7}{4}$

3. 最終的な答え

問題1：式の計算

(1) $-3x - 6y$

(2) $-5y^2 + 5y$

(3) $15a - 4b$

(4) $-x - 21y$

(5) $-6x + 44y$

(6) $10m - 20n + 14$

(7) $4a^2 + 1.7a$

(8) $\frac{14}{3}x - 3y$

(9) $\frac{7a+20b}{12}$

(10) $-50mn$

(11) $-9b$

(12) $70y^2$

(13) $-\frac{a}{3}$

(14) $-24x^3y$

問題2：式の値

(1) $30$

(2) $29$

(3) $\frac{7}{4}$