Question

a number has 2 digits the digit at tense place is 4 times the digit at units place if 54 is subtracted from the number that digit are reversed find the number

Answer 1

Let U be the units digit 
Let T be the tens digit 

The original number is 10T + U 
The reversed number is 10U + T 

The difference is 54: 
10T + U - (10U + T) = 54 
9T - 9U = 54 
9(T - U) = 54 
T - U = 6 

We also know that T is 4U, so substitute: 
4U - U = 6 
3U = 6 
U = 2 

T = 4U = 8 

The number is 10T + U = 80+2 = 82 

Answer: 
82