Let m kg be the mass of the second cheerleader.
By definition, the spring constant is
[tex]k = \frac{(61 \, kg)(9.8 \, m/s^{2})}{0.058 \, m} = \frac{(61+m \, kg)(9.8 \, m/s^{2})}{0.058+0.042 \, m} [/tex]
Therefore
m + 61 = (0.1)*(1.0517 x 10³) = 105.172
m = 44.172 kg
Answer: 44.2 kg