Question 28376
{{{.07 * a + .10 * b = 640}}}
{{{.10 * a + .07 * b = 550}}}
multiply both sides of each equation by 100
{{{7 * a + 10 * b = 64000}}}
{{{10 * a + 7 * b = 55000}}}
multiply both sides of the 2nd equation by 7/10
{{{7a + (49/10) * b = 38500}}}
subtract from the 1st equation
{{{10 * b - 4.9 * b = 15500}}}
{{{5.5 * b = 25500}}}
{{{b = 5000}}}
substitute in the 1st equation
{{{7 * a + 50000 = 64000}}}
{{{7 * a = 14000}}}
{{{a = 2000}}}
these are the amounts to be invested in dollars