Technically you should use 150g of solution and heat capacity of 33.3% solution, every other approach is just an approximation.

150g and heat capacity of water is probably the closest you can get without consulting detailed tables.

Can you know the difference between toluene and benzoic acid (benzoate ion)?

Your explanation is just a mess - in point 1 (i) you use the numbers 1, 2, 3, and in point 2 (ii) you use the numbers 1a, 1b, 1c.

Difference between Toluene(C₆H₅CH₃) and benzoic acid(C₆H₅COOH).

 Benzoic acid is prepared by replacing 2 H⁺ atoms in CH₃ molecule of toluene by 2 O^-2 atoms.

NaOH also has a specific heat capacity.

Your post has more errors. You must check the original publication.
My advice to write a reaction and check the figures can help if this error occurred in the original work (but that's rarely the case). in addition, it will help to understand the meaning of equivalents very frequently used in the patent literature.

I'm asking this because I watched 3 youtube videos and each one explained it differently with different results

when we have let's say 50 grams of NaOH dissolved in 100g water and the temperature of the water increases by 17.5, and we are given that the heat capacity of water is 4.18 and we are required to find the enthalpy of dissolution

when we use deltaH=mC(deltaT)
in the m, do we use the total mass of solution or only the mass of water?
m=100 or 150? that makes a lot of difference!
one video used 100 and then only used the mass of NaOH to get the moles and then find the molar enthalpy, the other videos used 150 from the start as m...

any clear answer please?

thanks