This equation shows how a sapling's height depends on its age.
h = 2a+72
the variable a represents the age of the sapling in years, and the variable h represents the height of the sapling in inches.
how tall was the sapling when it was 5 years old.

82 inches

Step-by-step explanation:

the equation that defines the height of a sampling in function of its age is:

where is the height in inches, and is the age of the sapling.

Since we need to know the height of a sapling that is 5 years old, we have that:

so we substitute this value of into the equation for height:

the height of the 5 years old sanpling is 82 inches

the answer to the question is a  

it has the same slope and the same y-intercept.