Solution: Let the height of two oil tanks be m when the oil level is the same, and the oil poured into B tank be n. ..

The total volume of oil is 20X 15X7=2 100.

B after pouring, the oil quantity in the oil tank is 2 100-N,

Therefore, N= 15X 15XM=225M,

2 100-N = 20x 15XM = 300m，

After bringing N=225M into the above formula, we get:

2 100-225M=300M，

525M=2 100, M=4 (decimeter).

Answer: At present, the oil level of the two fuel tanks is 4 decimeters.