Step 1: Use the wave speed formula.
The speed \( v \) of a wave on a string is given by:
\[
v = \sqrt{\frac{T}{\mu}}
\]
where \( T \) is the tension and \( \mu \) is the linear mass density (\( \mu = \frac{m}{L} \)).
Step 2: Apply the values.
Given \( T = 50 \, \text{N} \), \( m = 0.035 \, \text{kg} \), and \( L = 3 \, \text{m} \), we find:
\[
\mu = \frac{0.035}{3} = 0.01167 \, \text{kg/m}
\]
Substituting into the formula for \( v \), we get:
\[
v = \sqrt{\frac{50}{0.01167}} = 15.4 \, \text{m/s}
\]