let's say the amounts invested are "a" and "b", at 10% and 4% respectively
so, we know the total investment was 53,500, thus their sum is just that much
a + b = 53500
and we also know, they yield an income of 4,030
now, how much is 10% of a? well 10/100 * a or 0.10a
how much is 4% of b? well, 4/100 * b or 0.04b
we know their yield is 4,030, thus 0.10a + 0.04b = 4030
thus [tex]\bf \begin{cases}
a+b=53500\implies \boxed{b}=53500-a\\\\
0.10a+0.04b=4030\\
----------\\
0.10a+0.04\left( \boxed{53500-a} \right)=4030
\end{cases}[/tex]
solve for "a", to see how much was invested at 10%
what about "b"? well, b = 53500 - a
