a : 18 = x rest 10 ==> a = 18x+10 |+8
a : 20 = y rest 12 ==> a = 20y+12 |+8
==> a + 18 = 18 (x + 1)
==> a + 18 = 20 ( y+1)
a + 8 = c.m.m.m.c. (18; 20)
a + 8 = 2^2 × 3^2 × 5
a + 8 = 4 × 9 × 5
a + 8 = 180
a = 180 - 8
a = 172 (numarul cautat)
Verificam:
172 : 18 = 9 rest 10
172 : 20 = 8 rest 12