Răspuns :
a - b = 18
a + b = 80
a = b + 18
2b + 18 = 80
2b = 80 - 18 = 62
b = 62 : 2 = 31
a = 31 + 18 = 49
a + b = 80
a = b + 18
2b + 18 = 80
2b = 80 - 18 = 62
b = 62 : 2 = 31
a = 31 + 18 = 49
a \----------\
}18 dif }80 suma
b \-----------\
80-18 =62 sg egale
62:2=31 a
31+18=49 b
}18 dif }80 suma
b \-----------\
80-18 =62 sg egale
62:2=31 a
31+18=49 b