Suppose there are 7X units in warehouse A and 3X units in warehouse B before transferring out.

After the transfer, there are 7X-30 pieces left in warehouse A and 3X+30 pieces left in warehouse B. ..

At this point, the number of two warehouses is equal,

That is: 7X-30=3X+30.

solve

X= 15

Therefore, warehouse A originally had 7* 15= 105, and warehouse B originally had 3* 15=45.