Given
The area of rectangle is given 78 sq.inches.
The length is one more than the twice the width.
Step-by-step explanation
To determine the dimensions of the rectangle.
Let the length be l and width be w.
Then the area of rectangle is

From the statement given, the equation formed is

Substitute the length relation in the area of rectangle

Solve the quadratic equation and find width w.

As width cannot be negative then width is 6 in.
And length is determined by

Answer
Hence the length is 13 in and width is 6 in.