My fourth number is 39 my fifth number is 43 what is my first number?

27

Step-by-step explanation:

When you add u subtract 39 from 43 u will get 4

Therefore u will subtract 4 from 39 to get the third number which is 35 then subtract 4 from it to get the second number which is 31 then subtract another 4 to get the first number that's 27

27

Step-by-step explanation:

39+4=43

27, 31, 35, 39, 43