carlos is hoping to save at least $200 in the next four weeks his mom gives him $30

If Carlos's mom gives him $30 every week for four weeks, he will have a total of 4 * $30 = $<<4*30=120>>120.

Since Carlos wants to save at least $200, he still needs to save $200 - $120 = $<<200-120=80>>80. Answer: \boxed{80}.