Answer:
-½(30) = -15
Step-by-step explanation:
Marta's pool decrees ½ inch each day, so that would be -½ each day. You would take that -½ and multiply it by 30 so you can find out the decrees in inches over 30 days so the equation would be -½ × 30 = -15 (im sorry if that didn't make sense)