Реши уравнение с комментированием и сделай проверку: a) (180 : a + 15 ⋅ 3) : 8 = 6; б) 320 – (b ⋅ 4 + 120) : 5 = 240; в) 450 : (18 – y : 7) = 50; г) 5 ⋅ (810 : 9 – x ⋅ 3) = 315.

1. Решим уравнение a):
   1. (180 : a + 15 ⋅ 3) : 8 = 6
   2. 180 : a + 45 = 6 ⋅ 8
   3. 180 : a + 45 = 48
   4. 180 : a = 48 - 45
   5. 180 : a = 3
   6. a = 180 : 3
   7. a = 60
2. Решим уравнение б):
   1. 320 – (b ⋅ 4 + 120) : 5 = 240
   2. (b ⋅ 4 + 120) : 5 = 320 - 240
   3. (b ⋅ 4 + 120) : 5 = 80
   4. b ⋅ 4 + 120 = 80 ⋅ 5
   5. b ⋅ 4 + 120 = 400
   6. b ⋅ 4 = 400 - 120
   7. b ⋅ 4 = 280
   8. b = 280 : 4
   9. b = 70
3. Решим уравнение в):
   1. 450 : (18 – y : 7) = 50
   2. 18 – y : 7 = 450 : 50
   3. 18 – y : 7 = 9
   4. y : 7 = 18 - 9
   5. y : 7 = 9
   6. y = 9 ⋅ 7
   7. y = 63
4. Решим уравнение г):
   1. 5 ⋅ (810 : 9 – x ⋅ 3) = 315
   2. 810 : 9 – x ⋅ 3 = 315 : 5
   3. 90 – x ⋅ 3 = 63
   4. x ⋅ 3 = 90 - 63
   5. x ⋅ 3 = 27
   6. x = 27 : 3
   7. x = 9

Ответ: a = 60, b = 70, y = 63, x = 9