In the equation \( 0.4 - 7x = 3 \), the constants are the numbers that do not change their value. Here, the constants are:
- \( 0.4 \)
- \( 3 \)
The term \(-7\) is the coefficient of the variable \(x\), not a constant.
Therefore, the constants in the equation are \( 0.4 \) and \( 3 \).