Substitution is the worst way to solve a system which
does not have any letters with coefficient of 1 or -1.
Such systems are much easier solved by elimination.

However, since you specified to do it by substitution,
I will do so, but it will be much more difficult, as
it will involve lots of work with fractions. Here goes:

Solve the first equation for x





Substitute  for 




Cancel the 2 into the 4 and get a 2 where the 4 is





Distribute to remove the parentheses:



Combine like terms:



Add -10 to both sides:



Divide both sides by 



Cancel the 's, and simplify the right side





Now we substitute  for  into





Cancel the 3 into the 





Simplify the compound fraction by multiplying
the numerator and denominator by the LCD of 5



Distribute the 5 into the parentheses, and write 10 for the
denominator :



Write 25 for 5*5 and cancel the 5's in the second
term on top:







We reduce the fraction:



So the solution is , 

But that is by far the hardest way to solve a 
system of equations which has none of the terms
x, -x, y, or -y.  The easist way would be the
elimination method.  

Edwin