Question

A number consists of two digits The digit at the ones place is 3 times the digit at the tens place if 36 is added to the number the digits are reversed find the number

Answer 1

original number
tens digit = x then ones digit = 3x
value of 10s digit = 10x 
value of 1s digit = 3x
number = 10x + 3x = 13x

reversed number
10s digit = 3x and 1s digit = x
value of 10s digit = 30x
value of 1s digit = x
number = 30x + x = 31x

relation between original and reversed number
original number + 36 = reversed number
13x + 36 = 31x
36 = 31x - 13x
36 = 18x
36/18 = x
x = 2

therefore;
original number = 13x = 13*2 = 26
reversed number = 62