i would use elimination
to solve for one variable in either equation, you would end up with fractions, and fractions are hard to work with.
take the firs equation. to solve for y
6x -2y =3
-2y = -6x+3
y = -6x/-2 +3/-2
the last term is a fraction and then we substitute it into the other equation.
multiply the first equation by 3 and the second equation by 2
18x -6y =9
10x+6y = 8
28x = 17
we do not deal with fraction until we solve
400000 * (1 + 0.32)^t
= 400000 * 1.32^t
60% of y is 72
25% of y is 30 so multiply 30 by 4 and you get 120. multiply 120 by .60 and that leaves you with 72 as your answer.