Answer:
208.7°C was the initial temperature of the limestone.
Step-by-step explanation:
Heat lost by limestone will be equal to heat gained by the water
![-Q_1=Q_2](https://img.qammunity.org/2021/formulas/chemistry/college/ow1n9dub3458enp0rshd98ad460cxjq6g7.png)
Mass of limestone =
![m_1=62.6 g](https://img.qammunity.org/2021/formulas/chemistry/high-school/u376v3hx3796765nl52e5o592gwi5u1cks.png)
Specific heat capacity of limestone =
![c_1=0.921 J/g^oC](https://img.qammunity.org/2021/formulas/chemistry/high-school/apf2yvot569s07ajuj75mc5cai5q7mfljf.png)
Initial temperature of the limestone =
![T_1=?](https://img.qammunity.org/2021/formulas/chemistry/high-school/dfgp1ld1z0y9igk3jepe557095nejce38x.png)
Final temperature =
=T = 51.9°C
![Q_1=m_1c_1* (T-T_1)](https://img.qammunity.org/2021/formulas/chemistry/college/d97qx8feycflvb1v8jn4snbnab8eg9ft8v.png)
Mass of water=
![m_2=75.0 g](https://img.qammunity.org/2021/formulas/chemistry/high-school/6a7l9rey6aak8bni1uhcuw3x5kklv74nky.png)
Specific heat capacity of water=
![c_2=4.186 J/g^oC](https://img.qammunity.org/2021/formulas/chemistry/high-school/jyjou1m29s0eshvafhzgsj6b864l0xf1n5.png)
Initial temperature of the water =
![T_3=23.1^oC](https://img.qammunity.org/2021/formulas/chemistry/high-school/l2rkbcqxq716hotomgz4xk10lae739dxd1.png)
Final temperature of water =
=T = 51.9°C
![Q_2=m_2c_2* (T-T_3)](https://img.qammunity.org/2021/formulas/chemistry/college/am2r5v3udfo8aoub08tv4mwc078im4a5at.png)
![-Q_1=Q_2](https://img.qammunity.org/2021/formulas/chemistry/college/ow1n9dub3458enp0rshd98ad460cxjq6g7.png)
![-(m_1c_1* (T-T_1))=m_2c_2* (T-T_3)](https://img.qammunity.org/2021/formulas/chemistry/college/g2fcukcc0uxtamngbdgxa2z32bniwjebs8.png)
On substituting all values:
![-(62.6 g* 0.921 J/g^oC* (51.9^oC-T_1))=75.0 g* 4.186 J/g^oC* (51.9^oC-23.1^oC)](https://img.qammunity.org/2021/formulas/chemistry/high-school/hi66shsh8xjfxad43bhtcokjpf6ntdlf74.png)
![T_1=208.7^oC](https://img.qammunity.org/2021/formulas/chemistry/high-school/elgwuahomio4v5t94vt81ro9isonzfon1l.png)
208.7°C was the initial temperature of the limestone.