Yellowish spots under and above the leaves

Question

What are these yellowish spots under and above the bell pepper plant? And I can see black ants around these spots.

Answer 1

Those appear to be aphids, although the resolution of the photo leaves them a bit blurry under magnification. That would also explain the ants, since aphids secrete a sugar-like syrup known as honeydew which the ants like. It's probably easiest to remove them by hand, unless you have a lot of infected plants. You could also use insecticidal soap, but make sure that you cover the aphids with it (it's a contact pesticide) and don't apply during a sunny day (late in the day is okay).