Question

X Y
-2 5
-1 10
0 15
1 20
2 25

Write an equation that explains the relationship between the average X and average Y.

Answer 1

Sketch a graph of those points.
You will see immediately that x goes up by one while y goes up by 5 every time.
That means this is a straight line with constant slope 5/1 = 5
That means that an equation of form y = 5 x + b will fit all the points.
Use any point, for example (0,15) to find b
15 = 5*0 + b
b = 15
so our equation is
y = 5 x + 15