Question

Помогите чтобы было понятно

Answer 1

$900 \times (16 - c) = 5400 \\ 16 - c = 5400 \div 900 \\ 16 - c = 6 \\ c = 16 - 6 \\ c = 10 \\ 900 \times (16 - 10) = 5400 \\ 5400 = 5400 \\ \\ \\ 400 \times( x - 12) = 3600 \\ x - 12 = 3600 \div 400 \\ x - 12 = 9 \\ x = 9 + 12 \\ x = 21 \\ 400 \times (21 - 12) = 3600 \\ 3600 = 3600$

Answer 2

$900 \times (16 - c) = 5400 \\ 16 - c = 6 \\ - c = 6 - 16 \\ - c = - 10 \\ c = 10$
$400 \times (x - 12) = 3600 \\ x - 12 = 9 \\ x = 9 + 12 \\ x = 21$