1. В H₂CrO₄: \( 2(+1) + x + 4(-2) = 0 \) → \( 2 + x - 8 = 0 \) → \( x = +6 \).
2. В CrO: \( x + (-2) = 0 \) → \( x = +2 \).
3. В Cr₂O₃: \( 2x + 3(-2) = 0 \) → \( 2x - 6 = 0 \) → \( 2x = +6 \) → \( x = +3 \).
Ответ: 4) + 6; +2; +3