How do you know when a mapping diagram, ordered pair, table or graph is a function

Jayda's house is located at (1, 5). she can walk in a straight line to get to cristian's house. a fast-food restaurant is located at (11, 0) and partitions the way from jayda's house to cristian's house by a ratio of 5: 1. find the coordinate of cristian's house. me . im a little stuck

Jonathan pays $1.90 per pound for potatoes. he buys 8.3 pounds of potatoes. he determines that he will pay $15.77, before tax, for the potatoes. which best describes the reasonableness of jonathan’s solution? jonathan’s answer is reasonable because there are two decimal places in the factors and two in the product. jonathan’s answer is unreasonable because there are three decimal places in the factors and two in the product. jonathan’s answer is reasonable because is 16, and 16 is close to 15.77. jonathan’s answer is unreasonable because is 8, and 8 is not very close to 15.77.

For what values of x is x2 + 2x = 24 true?