So trump says the Yuan is artificially low and its making Chinese exports to cheep whilst making it too difficult for the USA to sell to China
Puts tariffs in place - Yuan goes down and offsets the tariffs making Chinese exports the same price for consumers in the states (but even more profitable for exporters) yet making it even harder for the USA to export to China
Plus all the USA debt they hold in $ (around 1.1 trillion) is revalued at en even higher price in Yuan
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Can see trump making a $1000 dollar note (with his picture on) and printing so many it makes the $ worthless - its honestly his only way out of the 4.4 trillion debt in the end if he wants low taxes and trade wars