Jack is 15 years younger than Sydney, The sum of their ages is 57. What is Sydney’s age?

I’m stuck on this i don’t understand.

Algebra 1: unit 6 part 2 of test a) the table shows a linear function. x 0 1 2 3 5 13 21 29 37 45 53 (a) determine the difference of outputs of any two inputs that are 1 unit apart. show your work. (b) determine the difference of outputs of any two inputs that are 2 units apart. show your work.

Of four points are collinear, they are also coplanar