460 and 375 are the answer.
Only 25 and 28 are functions.
A function must have only one y value per x value. For 26, the y value of 0 and multiple others have two different y values. For 27, all x values less than 0 have multiple y values.
7/10x - 5 = 1/2x
7/10x - 1/2x = 5
7/10x - 5/10x = 5
2/10x = 5
x = 5 / (2/10)
x = 5 * 10/2
x = 50/2
x = 25 gallons <===
2,3,4,1, the probability is in order from greatest to least. If they asked for least to greatest then, 1,4,3,2. So use the least to greatest one.