Question 414384
I'm guessing that the 2's are exponents. If this is correct, please use the "^" character to indicate exponents: 
3x^2-y^2<br>
I'm also guessing the problem is to evaluate the expression when x = 1/2 and y = 1/3. To do this we just substitute the values for x and y and use the order of operations (aka PEMDAS) to simplify:
{{{3x^2-y^2}}}
{{{3(1/2)^2-(1/3)^2}}}
Note the use of parentheses. This is a good habit whenever you are substituting one expression for another.
Next, according to the order of operations we should exponentiate:
{{{3(1/4)-(1/9)}}}
Next, multiply:
{{{3/4-1/9}}}
and last, subtract. Since these are fractions we need common denominators:
{{{(3/4)(9/9)-(1/9)(4/4)}}}
{{{27/36-4/36}}}
{{{23/36}}}