Answer:
y=6
Step-by-step explanation:
The equation of the line with slope 2 is y=2x+b, b is a constant which should be determined. The line passes via through points (1, 2) and (3,y)
(1, 2): 2=2+b --> b=0
So, the equation of the line is y=2x. Now, when x=3, y=6. So the line y=2x passes through points (1, 2) and (3, 6). (3,y)=(3, 6).
Answer: 
Step-by-step explanation:
Given
Cost per student in the year 1978 is $2200
The cost increases to $10,300 in 2008
Suppose
is the linear equation defining the cost per student after x years
Substitute the value for 1978

After 30 years it becomes

Thus, the linear equation becomes
