Repeat Yourself
1. Take any two digit number.
2. Multiply by 15.
3. Multiply by 7.
4. Subtract 4 times your original number.
Why are you repeating yourself?
Start over
1. Take any two digit number.
2. Multiply by 13.
3. Multiply by 8.
4. Subtract 3 times your original number.
Why don't you use some algebra to prove it?
Then following the instructions above:
1. Let x = original number.
2. Multiply by 15: 15x
3. Multiply by 7: 105x
4. Subtract 4 times your original number. 105x - 4x = 101x
(The 101 just moves the 2-digit number over 2 places and adds the number)
When you start over,
1. Let x = original number.
2. Multiply by 13: 13x
3. Multiply by 8: 104x
4. Subtract 3 times your original number. 104x - 3x = 101x
(The 101 just moves the 2-digit number over 2 places and adds the number)