Помогите пожалуйста с уравнениями даю 98 баллов

$2 \times x = 840 \\ x = 840 \div 2 \\ x = 420 \\ 2 \times 420 = 840 \\ 840 = 840 \\ \\ \\ x \div 19 = 19 \\ x = 19 \times 19 \\ x = 361 \\ 361 \div 19 = 19 \\ 19 = 19 \\ \\ \\ x \div 3 - 18 = 12 \\ x \div 3 = 12 + 18 \\ x \div 3 = 30 \\ x = 30 \times 3 \\ x = 90 \\90 \div 3 - 18 = 12 \\ 12 = 12 \\ \\ \\ 120 \div (25 - x) = 10 \\ 25 - x = 120 \div 10 \\ 25 - x = 12 \\ x = 25 - 12 \\ x = 13 \\120 \div (25 - 13) = 10 \\ 10 = 10 \\ \\ \\ x \times 5 + 80 = 690 \\ x \times 5 = 690 - 80 \\ x \times 5 = 610 \\ x = 610 \div 5 \\ x = 122 \\122 \times 5 + 80 = 690 \\ 690 = 690 \\ \\ \\ (708 - x) + 130 = 500 \\ 708 - x = 500 - 130 \\ 708 - x = 370 \\ x = 708 - 370 \\ x = 338 \\ (708 - 338) + 130 = 500 \\ 500 = 500$

Удачи!!!