A two digit number, exchange its ten digit number and one digit number, and the two digit number obtained is four times seven times of the original number. How many such two digits are there? speed

A two digit number, exchange its ten digit number and one digit number, and the two digit number obtained is four times seven times of the original number. How many such two digits are there? speed

Let the original two digit ten digit number be x and the single digit number be y
Then, 0