let's call the number "n", so we have a short term to talk about it
n will not exactly divisible by 5, because the remainder would be zero then.
since the remainder is 3, the number will be an integer that satisfies n = 5x + 3
example for 2x:
n = 5*2 + 3 = 13
if we devide 13 by 5, we would get 3 as remainder.
here the quotient would be 2 (the solution you get by dividing two numbers)
"x" is the quotient, so let's set it as 8
n = 5*8 +3
n = 43
checking it:
devide 43 by 5, you'll get 8 as the quotient and 3 as remainder.
hope it helps. Feel free to ask any question.