Question 186850
"the sum of the digits of a two-digit number is 6" ---> t+u=6 ---> t=6-u


"if the digits are reversed, the new number is three times the original tens digit" 10u+t=3t


10u+t=3t


10u=2t



10u=2(6-u)


10u=12-2u


12u=12


u=1


t=6-u


t=6-1


t=5



Original Number: 51