The perimeter of the triangle is the distance around it.
In the case of our triangle, the distance around it is
which we are told is 40 units; therefore,
Simplifying the expression on the left side of the equation (adding like terms) gives us
Now we solve for a by adding 2 to both sides of the equation and then dividing by 7:
Now we are in a position to compute the length of the longest side.
The longest side is 3a+1 and it evaluates to
The longest side is 19 units.
The shortest side is 2a-3 and it evaluates to
The shortest side is 9 units.
Therefore, the difference of length between the longest side and the shortest side is
Hence, the longest side is 10 units bigger than the shortest side.