The Scottish government said the price of a single passenger fare will fall by an average of 44% and car fares will be cut by an average of 55%.
The reduced fares will be introduced in October.
They will be the first routes to offer RET since Arran was added to the scheme last year.
The new RET routes include Mallaig to Armadale and Oban to Craignure.
Also services to Barra, Mull, Eigg, Skye, Raasay, Cumbrae, Muck and Rum.
RET was first introduced on Western Isles, Coll and Tiree services in 2008.
It was expanded to Islay, Colonsay and Gigha in 2012 and was introduced for Arran in October last year.
RET, which links ferry fares to the cost of travelling an equivalent distance on land, covers fares for passengers, cars, small commercial vehicles and coaches.
How much ferry fares will fall by when road equivalent tariff (RET) is rolled out to all remaining Clyde and Hebrides routes have been confirmed.