A system of 2 equations in 2 unkowns

A college student earned $8200 during summer vacation working as a waiter in a restaurant. The student invested part of the money at 7% and the rest at 6%. If the student received a total of $528 in interest at the end of the year, how much was invested at 7%?

So far, I have x+y=8200
y=8200-x
0.07x + 0.06y=528
0.07x + 0.06(8200-y)=528
0.07x + 492 - 0.06y=528

Where do I go from there?

Thanks so much for your help!

This is where I would use substitution.

x + y = 8200
0.07x + 0.06y = 528

Rewrite the first equation in terms of one of the variable.s

y = 8200 - x

Now SUBSTITUTE for that in the other equation.

0.07x + 0.06(8200 - x) = 528
0.07x + 492 - 0.06x = 528
0.01x = 36
x = 3600

So the student invested 3600 at 7% and 8200 - 3600 = 4600 at 6%