a)4x+1/3x-5 + 2x/12x-20

For this one, I would reduce second fraction by multiplying by (1/2)/(1/2), which is essentially multiplying by 1, so it is allowed:

(4x+1)/(3x-5) + x/(6x-10)

Now, in order to get a common denominator, we have to multiply the first fraction by 2/2 to get the lcd of 6x-10:

(8x+2)/(6x-10) + x/(6x-10)

Now, we can add the numerators because both fractions have the same denominator:

(8x+2+x)/(6x-10)

which becomes:

(9x+2)/(6x-10)

I don't think this could be reduced anymore.