text: max wants to invest 18,000, some in stocks earning 6% annunally and the rest in bonds earning 3% annunally...? question reads:  define showing variables. write two equations. solve by substitution or elimination, showing all steps.   max wants to invest 18,000, some in stocks earning 6% annunally and the rest in bonds earning 3% annunally. how much should be invested at each rate to get interest totaling $975.00 annually from the two investments? define showing variables: let a = amount invested in stocks let b = amount invested in bonds  equation 1: a + b = $18 000 hence, a = 18 000 - b  equation 2: (0.06 x a) + (0.03 x b) = 975 [ie. 6% return on a $ amount of stocks, plus 3% return on $ amount of bonds, equals total desired return]  substitute into the equation that a = 18 000 - b: (0.06 x [18 000 - b]) + (0.03 x b) = 975  expands out to: 1080 - 0.06b + 0.03b = 975 b = $3 500 [ie. invest $3 500 in bonds]  substitute b = 3 500 back into equation 1: a + 3500 = 18 000  therefore 'a' = 14 500 [ie. invest $14 500 in stocks]