the units digit of two-digit number is 4 more than the tens digit. Seven times the tens digit is 4 more than 3 times the units digit. find the number

Question

the units digit of two-digit number is 4 more than the tens digit. Seven times the tens digit is 4 more than 3 times the units digit. find the number

Answer 1

let x be the unit digit and y the tens digit. Then

x=y+4

3x+4=7y

 

x-y=4

3x-7y=-4

 

Solve this simple system and you get x=8, y=4. So your number is 84.

My answer is wrong, Reverse the number, replace x by y!