Пожалуйста,6 класс!!!!!!!

№1.
Подчеркнуть одной чертой : 2х ; 31,2х
Подчеркнуть двумя чертами: (-20,13у) ; (-40 1/5 у)

№2.
- 8m - (-10m) +13m - 24m = (-8 + 10 +13 - 24)m = - 9m
1.25a+ 2a+(-0.85a) - (-3a) -3a = (1.25 + 2 -0.85 + 3 - 3)a = 2.4a
$\frac{11}{21}n - \frac{2}{21} n - \frac{19}{21}n + \frac{5}{21} n = \frac{11-2-19+5}{21} n = - \frac{5}{21} n$

№3.
$\frac{11}{20}a -1\frac{1}{5}b +1\frac{11}{30}a -\frac{1}{6}b = ( \frac{11}{20}+1 \frac{11}{30} )*a - ( 1\frac{1}{5} + \frac{1}{6})*b = \\ \\ = \frac{11*3+11*2}{60} *a - \frac{6*6 +1*5}{30}* b = \frac{55}{60} a - \frac{41}{30} b = \frac{11}{12} a - 1 \frac{11}{30} b$

$2.37t -s - \frac{1}{4}t - 0.25t + 1 \frac{3}{8} s = (2.37t - 0.25t - 0.25t) +(1 \frac{3}{8}s - s) = \\ \\ = 1.87 t + \frac{3}{8} s$

№4.
15(3х - 5) + 6(7-2х) = 15*3х + 15 *(-5) + 6*7 + 6*(-2х) =
= 45х - 75 +42 -12х = (45х - 12х) - (75 - 42) = 33х -33

-8(-6 + 4у) + 2(-18 - 11у) = - 8 *(-6) - 8 *4у + 2*(-18) + 2*(-11у) =
= 48 - 24у - 36 - 22у = (48 - 36) - (24у + 22у) = 12 - 46у