One strategy for Amazing Alex The Backyard level 2-17, called “The Catapult”, is to place the bowling ball just under the Play button in the top-right corner. This will fling the tennis ball up toward the green pipe, but it will usually hit the elbow if left unaltered. Instead, place a shelf just above the pipe to catch the ball, then another shelf to guide it into the basket.
If you have a different strategy for completing this level feel free to leave a comment below.