Three consecutive multiples of 5 have a sum of 75. What is the least number?

If we let x equal the first number, then the next number has to be x + 5 (since they are multiples of 5) and the next would be x + 10. Now we just add them and set them equal to 75 ...

x + x+5 + x+10 = 75

Combine like terms

3x + 15 = 75

subtract 15 from each side

3x = 60

divide each side by 3

x = 20

So the least number is 20

*Now let's check to make sure we are right ...

20 + 25 + 30 = 75

75 = 75 True ... It checks!