Question 156476
{{{4000*x + 6000*2*x = 640}}}
{{{4000*x + 12000*x = 640}}}
{{{16000*x = 640}}}
{{{x = 640 / 16000}}}
{{{x = .04}}}
{{{2*x = .08 }}}
to test the answer
{{{4000 * .04 + 6000 * .08 = 640}}}
interest rate at bank A is .04.
interest rate at bank B is .08.