Answer:
their car's number-plate is 255
Step-by-step explanation:
let x,y,z represent the three digits respectively
The given conditions are;
Sunday: if each of the three digits was less than 6
x,y,z < 6
Monday: if the 3-digit number was odd
z = odd numbers less that 6
Tuesday: if the sum of the three digits was greater than 10
x+y+z > 10
Wednesday: if the 3-digit number was a multiple of 3
x+y+z = divisible by 3
Thursday: if the sum of the three digits was less than 15
x+y+z < 15
Friday: if at least two of the three digits were the same
x
Saturday: if the 3-digit number was less than 500
x < 5
(x = 1 to 4)
Since
x+y+z > 10
x+y+z < 15
x+y+z = divisible by 3
Then x+y+z = 12
z is odd numbers less that 6
z = (1,3,5)
x = (1,2,3,4)
y = (1,2,3,4,5)
The only combination that satisfies other conditions is;
x = 2
y = 5
z = 5
their car's number-plate is 255
