To get the reciprocal, simply flip the numerator and denominator. The reciprocal of 3/10 is 10/3.
Start with

Expand both parentheses by multiplying both terms by the number outside:

Sum like terms:

Simplify the "+3" on both sides:

Subtract 2x from both sides:

Divide both sides by 2:

I think it is d I am not sure thought I am sorry