The answer depends quite a bit on the exact height difference between the two horizontal lines. So:
1) Not allowed, a san-tee can only have drainage into the side entry when the straight path is vertical (meaning at most 45 degrees from plumb). You could use a quarter bend into an upright combo if you have enough height.
2) The simple way to go as long as you have enough height difference to make a 22.5 or 45 degree elbow work. [I.e. that if you rotate the combo 22.5 and stick a street 22.5 in the side inlet, you're not already too high for the WC drain. If that would be too high, see the next answer.]
3) Other non-simple options: use a wye rolled up 45 degrees and a 60 degree elbow. Not sure if that would be higher than a combo rolled 22.5 with a 22.5 elbow. Or for subtle control with just a very slight height difference, you can use a wye, a 45 and a 22.5 and play with the angle between the two elbows, along with the amount you roll the wye. But at that point you'd typically just be better off dropping the end of the upper drain enough to allow the use of a combo with no elbows.
Cheers, Wayne
