Karl needs a total of $30 to buy a bike. He has $12. He can earn $6 an hour
babysitting. Which equation can be used to find the number of hours, h, Karl has to
babysit to have the money he needs?

30 - 6h + 12 = 0
6+ n = 12
6 + 12 h = 30
6 h + 12 = 30​