My 4-digit number is a palindrome (meaning, that it does not change if you write it backwards), and it has remainder 21 when you divide it by 100. What is my number?

1221

Step-by-step explanation:

Given : A  4-digit number is a palindrome .

If it has remainder 21 when you divide it by 100, then last two digits are 21.

So required palindrome =  _ _ 21

since palindrome does not change if you write it backwards, so first two numbers should be reverse of 21 = 12

hence, the complete palindrome = 1221

So the number is 1221.

3x + 4y -25 =0 represents the amount of change sianna should recieve