since the width is 4 centimeters more than 3/10 of the length, then 13 is 4 centimeters more than 3/10 of the length. 4 less than 13 is 9, so nine is 3/10 of the length. if 9 is 3/10, then 3 is 1/10 because 3/10 is three times 1/10. If 3 is 1/10, that means that 30 is the length because 1/10 multiplied by 10 is 10 tenths, or 1.
