Order 75% ,1/2, 0.375,5/8 from least to greatest

Which is an equation for the nth terms of the sequence 12,15,18,21

When y’all answer can y’all explain too !

Jackson earns $25 per hour as a tutor at the college library. he set a weekly spending budget of $130 each week and puts the remaining money in his savings account. how many hours must he work this week to have at least an extra $50 to put in his savings account