[tex]Part \ of\ 5000\ should\ be\ invested\ at\ 3\%\ and\ part\ at\ 5\%.\\\\ x-\ part\ of\ 5000\ invested\ at \3\%\\x*3\%+(5000-x)*5\%=275\\
0,03x+0,05(5000-x)=275\\
0,03x+0,05*5000-0,05x=275\\
-0,02x=275-250\\
-0,02x=-25\ |:-0,2\\\
x=125\\
5000-125=4875\\
125 \$\ should\ be\ at\ 3\%\ and\ 4875\ at \ 5\%.[/tex]