1) (1+8.1).SI = 1; 2) 80,a : 1'8-0,25 : 0,025 = 4; 3) 10'4 : 1'8 = 5'8; 4) 80,8 = 4; 5) 21'5: 1'1 + 1'354 = ; 6) 1000. Найдите корень уравнения: 1) 3(2x-8) = 18; 2) 180-5x=30; 3) 10x:5=20; 4) 5x-25=80; 5) 2(3+x)=4.

Решение:

1. \( 3(2x - 8) = 18 \)
   \( 6x - 24 = 18 \)
   \( 6x = 18 + 24 \)
   \( 6x = 42 \)
   \( x = 7 \)
2. \( 180 - 5x = 30 \)
   \( 180 - 30 = 5x \)
   \( 150 = 5x \)
   \( x = 30 \)
3. \( 10x : 5 = 20 \)
   \( 10x = 20 · 5 \)
   \( 10x = 100 \)
   \( x = 10 \)
4. \( 5x - 25 = 80 \)
   \( 5x = 80 + 25 \)
   \( 5x = 105 \)
   \( x = 21 \)
5. \( 2(3 + x) = 4 \)
   \( 6 + 2x = 4 \)
   \( 2x = 4 - 6 \)
   \( 2x = -2 \)
   \( x = -1 \)

Ответ: 1) x = 7; 2) x = 30; 3) x = 10; 4) x = 21; 5) x = -1.