Упражнение «Пропущенные числа». Задание — вставить числа вместо вопросительных знаков. Время на выполнение всего упражнения – 5 минут. 19+?:5=22; 87-9x?=69; 21+54:?=27; 22:2x?=77; 112+?-68=82; 241-15x?=136; 315+?:9=324; 63:7x?=99; 208+64:?=240; 414-?x2=228; 313+66x?=425; 94:2-?=29

Решение:

1. \( 19 + x : 5 = 22 \) → \( x : 5 = 22 - 19 \) → \( x : 5 = 3 \) → \( x = 3 \cdot 5 = 15 \)
2. \( 87 - 9 \cdot x = 69 \) → \( 9 \cdot x = 87 - 69 \) → \( 9 \cdot x = 18 \) → \( x = 18 : 9 = 2 \)
3. \( 21 + 54 : x = 27 \) → \( 54 : x = 27 - 21 \) → \( 54 : x = 6 \) → \( x = 54 : 6 = 9 \)
4. \( 22 : 2 \cdot x = 77 \) → \( 11 \cdot x = 77 \) → \( x = 77 : 11 = 7 \)
5. \( 112 + x - 68 = 82 \) → \( 112 - 68 + x = 82 \) → \( 44 + x = 82 \) → \( x = 82 - 44 = 38 \)
6. \( 241 - 15 \cdot x = 136 \) → \( 15 \cdot x = 241 - 136 \) → \( 15 \cdot x = 105 \) → \( x = 105 : 15 = 7 \)
7. \( 315 + x : 9 = 324 \) → \( x : 9 = 324 - 315 \) → \( x : 9 = 9 \) → \( x = 9 \cdot 9 = 81 \)
8. \( 63 : 7 \cdot x = 99 \) → \( 9 \cdot x = 99 \) → \( x = 99 : 9 = 11 \)
9. \( 208 + 64 : x = 240 \) → \( 64 : x = 240 - 208 \) → \( 64 : x = 32 \) → \( x = 64 : 32 = 2 \)
10. \( 414 - x \cdot 2 = 228 \) → \( x \cdot 2 = 414 - 228 \) → \( x \cdot 2 = 186 \) → \( x = 186 : 2 = 93 \)
11. \( 313 + 66 \cdot x = 425 \) → \( 66 \cdot x = 425 - 313 \) → \( 66 \cdot x = 112 \) → \( x = 112 : 66 \) → \( x = \frac{112}{66} = \frac{56}{33} \)
12. \( 94 : 2 - x = 29 \) → \( 47 - x = 29 \) → \( x = 47 - 29 = 18 \)

Ответ: 15, 2, 9, 7, 38, 7, 81, 11, 2, 93, 56/33, 18.