Answer
$ \{ 80, 20 \}$
Work Step by Step
We can write the system of equations as:
$0.8 x+0.6 y=76~~~(1) \\ x+ y=100 ~~~(2)$
Equation (2) can be re-written as: $y=100-x$
Plug $y=100-x$ in equation (1) to obtain:
$0.8 x+0.6 (100-x)=76 \implies x=80$
Now, equation (2) becomes: $y=100-80=20$
Therefore, a solution set is $ \{ 80, 20 \}$
