An office used three types of envelopes: small, medium and large. They used 160 small envelopes. The no. of medium envelopes used was 5 times the no. of small envelopes plus 5/20 of the total no. of the envelopes. The no. of large envelopes was equal to the no. of small envelopes plus 5/20 of the no. of medium envelopes. Altogether, How many envelop did they use?