Does the table represent a function?how do you know

Need plz been trying to do it for a long time and still haven’t succeeded

Of jk j(–25, 10) k(5, –20). is y- of l, jk a 7: 3 ? –16 –11 –4 –1

The students at jefferson middle school are raising money for a charity by selling t-shirts and hats. the number of t-shirts sold was 3 times the number of hats. the profit was $5 for each t-shirt sold and $2.50 for each hat sold. the students raised $840 for the charity. they used the system below to analyze their success and found the solution to be (144, 48). 5x+2.50y=840 x=3y how much did they earn from t-shirt sales?