What will be the freezing point of a 5 m aqueous solution of ki? water kf = 1.86 ºc/m?

This is a problem involving colligative properties. For problems involving freezing point depression, the formula is as follows:

Tfp,solvent  - Tfp,solution = iKfm
For KI solution, the solvent is water. So, the freezing point of water, Tfp,solvent = 0°C. The i is the number of ions dissociated. In this case, i = 2 (1 for K⁺ and 1 for I⁻).

0 - Tfp,solution = (2)(1.86 ºc/m)(5 m)
Tfp,solution = -18.6°C

1. and 2. question: in which equation? or i don't understand you, 3. a), 4. c), 5. c), 6. b), 7. d), 8. d) if small number is underlined(behind symbol) , b) if big number is underlined(in front of symbol)9. what is underlined there? 10. c)