Context clues can help you figure out the meaning of a word or phrase you don’t know. These clues can be found in the words and sentences surely the unknown word or phrase.
y = 7x - 15
Since you're solving for the y-intercept, the value of x is zero.
y = 7(0) - 15
y = 0 - 15
y = -15
To endure unnecessary inconvinience.