Let the one’s digit be ‘a’ and ten’s digit be ‘b’
Given, number is 4 times the sum of its digits.
10b + a = 4(a + b)
⇒ a = 2b -----(1)
Also, if 18 is added to the number, the digits are reversed.
⇒ 10b + a + 18 = 10a + b
⇒ a – b = 2 ----- (2)
Substituting a from eq1 in eq2
⇒ b = 2
Thus, a = 4
Number is 24