Question 927571
Let  x be the amount invested in an account that paid 7 % per year
 Let y be the amount invested  in an account that paid  12 % per year
 x+y= $ 5000.......................eq(1)
interest on amount  = 10 % of X
                     ={{{ (7/100)8x}}}
                     {{0.07x}}}
Interest on amount y = 12 % of y
                      = {{{ (12/100)*y}}}
                      ={{{0.12y}}}
Total interest for whole amount  = $ 400
hence 
         0.07 x+0.12 y =400.............eq(2)
solve eq(1) and eq(2) to get x& Y values*[invoke linear_substitution "x", "y", 1, 1, 5000, 0.07, 0.12, 400 ]
Result":

X=  $4000
y= $1000