Let x be the amount invested at 6% so that 18000-x is the amount invested at 7.5% both in dollars.

The total interest in 2 years is $2220 so we can write: 0.06x(2)+0.0075(18000-x)(2)=2220

Solve for x:

0.12x+2700-0.15x=2220

-0.03x+2700=2220

-0.03x=-480

\(\displaystyle{x}=-\frac{{480}}{{-{{0.03}}}}\)

x=16000

So, the amounts borrowed are:

Bank at \(\displaystyle{6}\%\to\${16000}\)

Bank at \(\displaystyle{7.5}\%\to{2000}\)

The total interest in 2 years is $2220 so we can write: 0.06x(2)+0.0075(18000-x)(2)=2220

Solve for x:

0.12x+2700-0.15x=2220

-0.03x+2700=2220

-0.03x=-480

\(\displaystyle{x}=-\frac{{480}}{{-{{0.03}}}}\)

x=16000

So, the amounts borrowed are:

Bank at \(\displaystyle{6}\%\to\${16000}\)

Bank at \(\displaystyle{7.5}\%\to{2000}\)