x - ilosc wagonów 10-cio tonowych
y - ilość wagonów 15-sto tonowych
x + y = 59
10x + 15y = 800 /:5
x = 59-y
2x + 3y = 160
x = 59 - y
2(59-y) +3y = 160
x = 59 - y
118 - 2y + 3y = 160
x = 59 - y
118 + y = 160
x = 59 - y
y = 42 (160 - 118 = 42)
x = 17
y = 42