In a two-digit number, the tens digit is 4 more than the units digit. The number is 7 less than 8 times the sum of the digits. Find the number.

Answer 1

n = units digit

n + 4 = tens digit

The number must be 10(n + 4) + n. That must also equal 8[(n + 4) + n] - 7.

10(n + 4) + n = 8[(n + 4) + n] - 7

11n + 40 = 16n + 25

15 = 5n

n = 3

n + 4 = 7

The number is 73. Test the answer.