Răspuns:
fie x suma cheltuita; fie a suma cheltuita in prima zi; b suma cheltuita in a doua zi si c suma cheltuita in a treia zi
x=a+b+c
a=40% din x= 2/5*x
b=60% din (x-2/5x) = 3/5 * 3/5x= 9/25 x
c=a- 40 = 2/5x - 40
x= 2/5 x + 9/25 x + 2/5x -40 = | *25
25x = 10x + 9x + 10x - 1000
=> 25x = 29x - 1000 | -29x
=> -4x = -1000 | :4
=> -x= - 250 => x=250 suma de bani era 250 lei