To solve the equation \( \frac{3}{7}c = -\frac{2}{7} \), we can isolate \( c \) by multiplying both sides of the equation by the reciprocal of \( \frac{3}{7} \).
This means we will multiply both sides by \( \frac{7}{3} \):
\[ c = -\frac{2}{7} \times \frac{7}{3} \]
Now simplify the right-hand side:
\[ c = -\frac{2 \times 7}{7 \times 3} \]
The \( 7 \) in the numerator and the \( 7 \) in the denominator cancel out:
\[ c = -\frac{2}{3} \]
So the solution is:
\[ c = -\frac{2}{3} \]