Solution: If the original price of commodity A is 7X yuan and the original price of commodity B is 3X yuan, we can get:

(70+7X ) :(3X+70)=7:4，

The solution is X=30, 7X=2 10, 3X=90.

A: the original price of a commodity is 2 10 yuan, and the original price of b commodity is 90 yuan.

Hope to adopt. Thank you.