3+|5х+2,1|=0,7

To solve the equation \( 3 + |5x + 2.1| = 0.7 \), we first isolate the absolute value:

\[ |5x + 2.1| = 0.7 - 3 \]

This simplifies to:

\[ |5x + 2.1| = -2.3 \]

Since the absolute value cannot be negative, there are no solutions to the equation \( 5x + 2.1 \) such that \( |5x + 2.1| = -2.3 \).

Thus, the conclusion is that there are no solutions.