1 Задача: Решите уравнение. a)-45a + 720 = -5a г) 54-9d = 36 - 11d 6) 7b = -280 + 3b д) 31 + 25y = 321 + 15y в) -6с +95 = 4c - 55 e) 18x - 42 = 10x - 18

Решение:

1. а) -45a + 720 = -5a
   \( -45a + 5a = -720 \)
   \( -40a = -720 \)
   \( a = \frac{-720}{-40} \)
   \( a = 18 \)
2. б) 7b = -280 + 3b
   \( 7b - 3b = -280 \)
   \( 4b = -280 \)
   \( b = \frac{-280}{4} \)
   \( b = -70 \)
3. в) -6с + 95 = 4c - 55
   \( 95 + 55 = 4c + 6c \)
   \( 150 = 10c \)
   \( c = \frac{150}{10} \)
   \( c = 15 \)
4. г) 54 - 9d = 36 - 11d
   \( -9d + 11d = 36 - 54 \)
   \( 2d = -18 \)
   \( d = \frac{-18}{2} \)
   \( d = -9 \)
5. д) 31 + 25y = 321 + 15y
   \( 25y - 15y = 321 - 31 \)
   \( 10y = 290 \)
   \( y = \frac{290}{10} \)
   \( y = 29 \)
6. е) 18x - 42 = 10x - 18
   \( 18x - 10x = 42 - 18 \)
   \( 8x = 24 \)
   \( x = \frac{24}{8} \)
   \( x = 3 \)

Ответ: а) a = 18; б) b = -70; в) c = 15; г) d = -9; д) y = 29; е) x = 3.