+36916 add the two equations to get 2x = sqrt31 + sqrt21 x = 1/2 ( sqrt31+sqrt21)
multiply second equation by -1 to get -x+y = -sqrt21 add to first equation to get
2 y = sqrt31 - sqrt21
y = 1/2 (sqrt31 - sqrt21)
multiply the red equations together 31/4 - 21/4 = 10/4 = 2.5
