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