text: Define showing variables:\nLet a = amount invested in stocks\nLet b = amount invested in bonds\n\nEquation 1:\na + b = $18 000\nhence, a = 18 000 - b\n\nEquation 2:\n(0.06 x a) + (0.03 x b) = 975\n[ie. 6% return on a $ amount of stocks, plus 3% return on $ amount of bonds, equals total desired return]\n\nSubstitute into the equation that a = 18 000 - b:\n(0.06 x [18 000 - b]) + (0.03 x b) = 975\n\nExpands out to:\n1080 - 0.06b + 0.03b = 975\nb = $3 500\n[ie. invest $3 500 in bonds]\n\nSubstitute b = 3 500 back into Equation 1:\na + 3500 = 18 000\n\nTherefore 'a' = 14 500\n[ie. invest $14 500 in stocks]