Evan has a cell phone plan that costs $30 per month and $0.25 per minute of phone use, the expression to find out how much money he has to pay total would be y=30+0.25x (The first choice would be correct)
This expression is correct because if you use substitution to figure it out more real world then the problem becomes easier. For instance, lets say he spends 20 minutes on the cell phone. Then he would have to pay $0.25 per minute. And pay the addition overall charge of $30. y is the total amount payed.
If x=20 (because lets say he used 20min)
y=30+0.25(20)