How would i tansmission a 7:3(torque) to a 7:1(torque)?
there are several ways, if you have pneumatics, you can do a pnumatic one, which is this Vex 2 Speed Transmission Working Prototype - YouTube
(which is probably the best way)
or you could do a differential
VEX Differential-Based Two-Speed Transmission - YouTube
(which requires more parts is more complex and introduces more friction)
I think the key factor here is that he wants to change from 7:3 to 7:1. This is not a standard 1:3/3:1 or 1:5/5:1 transmission and requires a little more thought.
I don’t know of any way to make a transmission with that gear ratio change very easily. Usually, you want gear setups that have the shafts in the same place on both configurations.
Such as: 3:5/5:3, 7:3/3:7, or 3:3/5:1
On the 7:1 put an idler 12 tooth gear in there to make the axles line up. That would be the easiest way of doing it.