Let x be first digit and y be second digit of the number.

number = 10x + y

since x+y is 1/7 of number,

7(x+y) = 10x + y
7x + 7y = 10x + y
3x = 6y
x=2y

since number decreases by 36 when digits are reversed,
10y + x = 10x + y - 36
9y = 9x - 36

sub x = 2y into 9y =9x - 36

9y = 18y - 36
9y = 36
y = 4
x= 2y
x= 2(4)
x= 8

NUMBER = 84