Numerele x, y, z si t sunt invers proporționale cu 4, 5, 6 si 10, adica:
4x = 5y = 6z = 10t = k
De aici rezulta:
x = k/4
y = k/5
z = k/6
t = k/10
Înlocuim x, y, z si t in relatia:
2(x+y) - 5z + t = 10
2(k/4 + k/5) - 5×k/6 + k/10 = 10
2(5k/20 + 4k/20) - 5k/6 + k/10 = 10
2×9k/20 - 5k/6 + k/10 = 10
9k/10 - 5k/6 + k/10 = 10
10k/10 - 5k/6 = 10
k/1 - 5k/6 = 10
6k/6 - 5k/6 = 10
k/6 = 10/1
k = 6×10/1
k = 60
Putem afla acum x, y, z si t:
x = k/4 = 60/4 = 15
y = k/5 = 60/5 = 12
z = k/6 = 60/6 = 10
t = k/10 = 60/10 = 6
